Asciidoctor PDF: A native PDF converter for AsciiDoc

Lo and behold, a native PDF converter for AsciiDoc built with Asciidoctor and Prawn!
No more middleman.
No more DocBook toolchain.
It’s AsciiDoc straight to PDF!

Prawn, the Majestic PDF Generator
Highlights
Prerequisites
Getting Started
Themes
Font-Based Icons
Image Paths
Image Scaling
Background Image Positioning
Fonts in SVG Images
Supporting Additional Image File Formats
STEM Support
Skipping Passthrough Content
Shaded Blocks and Performance
Autofitting Text
Printing Page Ranges
Title Page
Table of Contents
Index Catalog
Optimizing the Generated PDF
Contributing
Development
Resources
Authors
Copyright

Prawn, the Majestic PDF Generator

Asciidoctor PDF is made possible by an amazing Ruby gem named Prawn. And what a gem it is!

Prawn is a nimble PDF writer for Ruby. More important, it’s a hackable platform that offers both high level APIs for the most common needs and low level APIs for bending the document model to accommodate special circumstances.

With Prawn, you can write text, draw lines and shapes and place images anywhere on the page and add as much color as you like. In addition, it brings a fluent API and aggressive code re-use to the printable document space.

Here’s an example that demonstrates how to use Prawn to create a basic PDF document.

Create a basic PDF document using Prawn

require 'prawn'

Prawn::Document.generate 'output.pdf' do
  text 'Hello, PDF creation!'
end

It’s that easy. And that’s just the beginning. Skip ahead to Getting started to start putting it use.

Prawn is the killer library for PDF generation we’ve needed to close this critical gap in Asciidoctor. It absolutely takes the pain out of creating printable documents. Picking up from there, Asciidoctor PDF takes the pain out of creating PDF documents from AsciiDoc.

Highlights

Direct AsciiDoc to PDF conversion
Configuration-driven theme (style and layout)
SVG support
PDF document outline (i.e., bookmarks)
Table of contents page(s)
Document metadata (title, authors, subject, keywords, etc)
Internal cross reference links
Syntax highlighting with Rouge, Pygments, or CodeRay
Page numbering
Customizable running content (header and footer)
“Keep together” blocks (i.e., page breaks avoided in certain block content)
Orphaned section titles avoided
Autofit verbatim blocks (as permitted by base_font_size_min setting)
Table border settings honored
Font-based icons
Custom (TTF) fonts
Double-sided printing mode (margins alternate on recto and verso pages)

Prerequisites

All that’s needed is Ruby 2.3 or better and a few Ruby gems (including at least Asciidoctor 1.5.3), which we explain how to install in the next section.

To check if you have Ruby available, use the ruby command to query the version installed:

$ ruby --version

Make sure this command reports a Ruby version that’s at least 2.3. If so, you may proceed.

System Encoding

Asciidoctor assumes you’re using UTF-8 encoding. To minimize encoding problems, make sure the default encoding of your system is set to UTF-8.

If you’re using a non-English Windows environment, the default encoding of your system may not be UTF-8. As a result, you may get an Encoding::UndefinedConversionError or other encoding issues when invoking Asciidoctor. To solve these problems, we recommend at least changing the active code page in your console to UTF-8.

chcp 65001

Once you make this change, all your Unicode headaches will be behind you.

Getting Started

You can get Asciidoctor PDF by installing the published gem. You can also run the code from source if you want to use a development version or participate in development.

Install the Published Gem

Asciidoctor PDF is published to RubyGems.org as a pre-release. Since it’s in pre-release, you have to specify the --pre flag when installing using the gem command.

To install Asciidoctor PDF, first make sure you have satisfied the prerequisites. Then, install the gem from RubyGems.org using the following command:

$ gem install asciidoctor-pdf --pre

If you want to syntax highlight source listings, you’ll also want to install Rouge, Pygments, or CodeRay. Choose one (or more) of the following:

Rouge (preferred, minimum version: 2.0.0)

$ gem install rouge

Pygments

$ gem install pygments.rb

CodeRay

$ gem install coderay

You then activate syntax highlighting for a given document by adding the source-highlighter attribute to the document header (Rouge shown):

:source-highlighter: rouge

Run the Application

Assuming all the required gems install properly, verify you can run the asciidoctor-pdf script:

$ asciidoctor-pdf -v

If you see the version of Asciidoctor PDF printed, you’re ready to use Asciidoctor PDF!

Let’s grab an AsciiDoc document to distill and start putting Asciidoctor PDF to use.

An Example AsciiDoc Document

If you don’t already have an AsciiDoc document, you can use the basic-example.adoc file found in the examples directory of this project.

See basic-example.adoc.

It’s time to convert the AsciiDoc document directly to PDF.

Convert AsciiDoc to PDF

❗	You’ll need the `rouge` gem installed to run this example since it uses the `source-highlighter` attribute with the value of `rouge`.

Converting to PDF is a simple as running the asciidoctor-pdf script using Ruby and passing our AsciiDoc document as the first argument.

$ asciidoctor-pdf basic-example.adoc

This command is just a shorthand way of running:

$ asciidoctor -r asciidoctor-pdf -b pdf basic-example.adoc

The asciidoctor-pdf command just saves you from having to remember all those flags. That’s why we created it.

When the script completes, you should see the file basic-example.pdf in the same directory. Open the basic-example.pdf file with a PDF viewer to see the result.

Figure 1. Example PDF document rendered in a PDF viewer

You’re also encouraged to try converting this README as well as the documents in the examples directory to see more of what Asciidoctor PDF can do.

The pain of the DocBook toolchain should be melting away about now.

Themes

The layout and styling of the PDF is driven by a YAML configuration file. To learn how the theming system works and how to create and apply custom themes, refer to the Asciidoctor PDF Theme Guide. You can use the built-in theme files, which you can find in the data/themes directory, as examples.

If you’ve enabled a source highlighter, you can control the style (aka theme) it applies to source blocks using the coderay-style, pygments-style, and rouge-style attributes, respectively. For example, to configure Rouge to use the built-in monokai theme, run Asciidoctor PDF as follows:

$ asciidoctor-pdf -a rouge-style=monokai basic-example.adoc

It’s possible to develop your own theme for Rouge. Refer to the Asciidoctor PDF Theme Guide for details.

Support for Non-Latin Languages

Asciidoctor can process the full range of characters in the UTF-8 character set. That means you can write your document in any language, save the file with UTF-8 encoding, and expect Asciidoctor to convert the text properly. However, you may notice that certain characters for certain languages, such as Chinese, are missing in the PDF. Read on to find out why and how to address it.

If you’re writing in a non-Latin language, you need to use a dedicated theme that provides the necessary fonts. For example, to produce a PDF from a document written in a CJK language such as Chinese, you need to use a CJK theme. You can get such a theme by installing the asciidoctor-pdf-cjk-kai_gen_gothic gem. See the asciidoctor-pdf-cjk-kai_gen_gothic project for detailed instructions.

Using a dedicated theme is necessary because PDF is a “bring your own font” kind of system. In other words, the font you provide must provide glyphs for all the characters. There’s no one font that supports all the worlds languages (though some, like Noto Serif, certainly come close). Even if there were such a font, bundling that font with the main gem would make the package enormous. It would also severely limit the style choices in the default theme, which targets Latin-based languages.

Therefore, we’re taking the strategy of creating separate dedicated theme gems that target each language family, such as CJK. The base theme for CJK languages is provided by the asciidoctor-pdf-cjk project and a concrete implementation provided by the asciidoctor-pdf-cjk-kai_gen_gothic project that’s based on the kai_gen_gothic font. Of course, you’re free to follow this model and create your own theme gem that uses fonts of your choice.

Font-Based Icons

You can use icons in your PDF document using any of the following icon sets:

fa - https://fontawesome.com/v4.7.0/icons (default)
fas - Font Awesome - Solid
fab - Font Awesome - Brands
far - Font Awesome - Regular
fi - Foundation Icons
pf - Payment font

The fa icon set is deprecated. Please use one of the other three FontAwesome icon sets.

You can enable font-based icons by setting the following attribute in the header of your document:

:icons: font

If you want to override the font set globally, also set the icon-set attribute:

:icons: font
:icon-set: pf

Here’s an example that shows how to use the Amazon icon from the payment font (pf) icon set in a sentence (assuming the icon-set is set to `pf):

Available now at icon:amazon[].

You can use the set attribute on the icon macro to override the icon set for a given icon.

Available now at icon:amazon[set=pf].

You can also specify the font set using the following shorthand.

Available now at icon:amazon@pf[].

In addition to the sizes supported in the HTML backend (lg, 1x, 2x, etc), you can enter any relative value in the size attribute (e.g., 1.5em, 150%, etc).

icon:android[size=40em]

You can enable use of fonts during PDF generation (instead of in the document header) by passing the icons attribute to the asciidoctor-pdf command.

$ asciidoctor-pdf -a icons=font -a icon-set=pf sample.adoc

Icon-based fonts are handled by the prawn-icon gem. To find a complete list of available icons, consult the prawn-icon repository.

Image Paths

Relative images paths in the document are resolved relative to the value of the imagesdir attribute (at the time the converter runs). This is effectively the same as how the built-in HTML converter works when the data-uri attribute is set. The imagesdir is blank by default, which means relative images paths are resolved relative to the input document. Relative images paths in the theme are resolved relative to the value of the pdf-themesdir attribute (which defaults to the directory of the theme file). The imagesdir attribute is not used when resolving an image path in the theme file. Absolute image paths are used as is.

If the image is an SVG, and the SVG includes a nested raster image (PNG or JPG) with a relative path, that path is resolved relative to the directory that contains the SVG.

The converter will refuse to embed an image if the target is a URI (including image references in an SVG) unless the allow-uri-read attribute is enabled via the CLI or API.

If you use a linked image in an SVG, the width and height of that image must be specified. Otherwise, the SVG library will fail to process it.

Asciidoctor Diagram Integration

As of Asciidoctor PDF 1.5.0.alpha.17 running on Asciidoctor 2 or better, Asciidoctor PDF provides better integration with Asciidoctor Diagram by setting the data-uri attribute by default. When the data-uri attribute is set, Asciidoctor Diagram returns the absolute path to the generated image, which Asciidoctor PDF can then locate. (This makes sense since technically, Asciidoctor Diagram must embed the image in the document, similar in spirit to the data-uri feature for HTML). This means the input directory and the output directory (and thus the imagesoutdir) can differ and Asciidoctor PDF will still be able to locate the generate image.

Prior to Asciidoctor PDF 1.5.0.alpha.17 (or prior to Asciidoctor 2), the way to solve this problem is to set the imagesdir attribute to an absolute path. That way, it won’t matter where the generated image is written. Asciidoctor PDF will still be able to find it. Keep in mind that this strategy may introduce other side effects you’ll have to work around.

Image Scaling

Since PDF is a fixed-width canvas, you almost always need to specify a width to get the image to fit properly on the page. There are five ways to specify the width of an image, listed here in order of precedence:

Attribute Name	Description
pdfwidth	The display width of the image as an absolute size (e.g., 2in), percentage of the content area width (e.g., 75%), or percentage of the page width (e.g., 100vw). If a unit of measurement is not specified (or not recognized), pt (points) is assumed. Intended to be used for the PDF converter only.
scaledwidth	The display width of the image as an absolute size (e.g., 2in) or percentage of the content area width (e.g., 75%). If a unit of measurement is not specified, % (percentage) is assumed. If a unit of measurement is recognized, pt (points) is assumed. Intended to be used for print output such as PDF.
image_width key from theme	Accepts the same values as pdfwidth. Only applies to block images.
width	The unitless display width of the image (assumed to be pixels), typically matching the intrinsic width of the image. If the width exceeds the content area width, the image is scaled down to the content area width.
*unspecified*	If you don’t specify one of the aforementioned width settings, the intrinsic width of the image is used (the px value is multiplied by 75% to convert to pt, assuming canvas is 96 dpi) unless the width exceeds the content area width, in which case the image is scaled down to the content area width.

The image is always sized according to the explicit or intrinsic width, then its height is scaled proportionally. The height of the image is ignored by the PDF converter unless the height of the image exceeds the content height of the page. In this case, the image is scaled down to fit on a single page.

If you want a block image to align to the boundaries of the page (not the content margin), specify the align-to-page option (e.g., opts="align-to-page"). This is most useful when using vw units because you can make the image cover the entire width of the page.

Images in running content and page background images also support the fit attribute (when specified using the image macro). If the value of this attribute is contain, the image size is increased or decreased to fill the available space while preserving its aspect ratio. If the value of this attribute is scaled-down, the image size is first resolved in the normal way, then scaled down further to fit within the available space, if necessary.

If sizing information is not specified for a page background image, the image is automatically scaled to fit the bounds of the page (i.e., fit=contain).

Using the pdfwidth Attribute

The pdfwidth attribute is the recommended way to set the image size for the PDF output. This attribute is provided for two reasons. First, the fixed-width canvas often calls for a width that is distinct from other output formats, such as HTML. Second, this attribute allows the width to be expressed using a variety of units.

The pdfwidth attribute supports the following units:

pt (default)
in
cm
mm
px
pc
vw (percentage of page width)
% (percentage of content area width)

In all cases, the width is converted to pt.

Specifying a default width

If you want to scale all block images that don’t have a pdfwidth or scaledwidth attribute specified, assign a value to the image_width key in your theme.

image:
  width: 100%

Inline Image Sizing

Inline images can be sized in much the same way as block images (using the pdfwidth, scaledwidth or width attributes), with the following exceptions:

The viewport width unit (i.e., vw) is not recognized in this context.
The image will be scaled down, if necessary, to fit the width and height of the content area.
Inline images do not currently support a default width controlled from the theme.

If the resolved height of the image is less than or equal to 1.5 times the line height, the image won’t disrupt the line height and is centered vertically in the line. This is done to maximize the use of available space. Once the resolved height exceeds this amount, the height of the line is increased (by increasing the font size of the invisible placeholder text) to accommodate the image. In this case, the surrounding text will be aligned to the bottom of the image. If the image height exceeds the height of the page, the image will be scaled down to fit on a single page (this may cause the image to advance to the subsequent page).

Background Image Sizing

In addition to the width-related attributes previously covered, background images can be sized relative to the page using the fit attribute of the image macro. The fit attribute works similarly to the object-fit property in CSS. It’s value must be specified as a single keyword, chosen from the table below. The starting size of the image is determined by the explicit width, if specified, or the implicit width. The height is always derived from with width, respecting the implicit aspect ratio of the image. The available space for a background image (i.e., the canvas) is the page.

Value	Purpose
contain	The image is scaled up or down while retaining its aspect ratio to fit within the available space.
cover	The image is scaled up or down while retaining its aspect ratio so the image completely covers the available space, even if it means the image must be clipped in one direction.
scale-down	The image is scaled down while retaining its aspect ratio to fit within the available space. If the image already fits, it is not scaled.
none	The image is not scaled.

The fit attribute is often combined with the position attribute, covered next, to control the placement of the image on the canvas.

Background Image Positioning

In addition to scaling, background images for cover pages, content pages, and the title page support positioning via the position attribute. The position attribute accepts a syntax similar to the background-position property in CSS, except only the keyword positions are supported. The position consists of two values, the vertical position and the horizontal position (e.g., top center). If only one value is specified (e.g., top), the other value is assumed to be center. If the position attribute is not specified, the value is assumed to be center center (i.e., the image is centered on the page).

The following table provides a list of the vertical and horizontal positioning keywords that are supported. You can use any combination of these keywords to position the image.

Vertical Positions	Horizontal Positions
top center bottom	left center right

Here’s an example of how to place a background image at the top center of every page:

:page-background-image: image:bg.png[pdfwidth=50%,position=top]

Here’s how to move it to the bottom right:

:page-background-image: image:bg.png[pdfwidth=50%,position=bottom right]

If an image dimension matches the height or width of the page, the positioning keyword for that axis has no effect.

Fonts in SVG Images

Asciidoctor PDF uses prawn-svg to embed SVGs in the PDF document, including SVGs generated by Asciidoctor Diagram.

Actually, it’s not accurate to say that prawn-svg embeds the SVG. Rather, prawn-svg is an SVG renderer. prawn-svg translates an SVG into native PDF text and graphic objects. You can think of the SVG as a sequence of drawing commands. The result becomes indistinguishable from other PDF objects.

What that means for text is that any font family used for text in the SVG must be registered in the Asciidoctor PDF theme file (and thus with Prawn). Otherwise, Prawn will fallback to using the closest matching built-in (afm) font from PDF (e.g., sans-serif becomes Helvetica). Recall that afm fonts only support basic Latin. As we like to say, PDF is bring your own font.

If you’re using Asciidoctor Diagram to generate SVGs to embed in the PDF, you likely need to specify the default font the diagramming tool uses. Let’s assume you are making a plantuml diagram.

To set the font used in the diagram, first create a file named plantuml.cfg and populate it with the following content:

skinparam defaultFontName Noto Serif

💡	You can choose any font name that is registered in your Asciidoctor PDF theme file. When using the default theme, your options are "Noto Serif", "M+ 1mn", and "M+ 1p Fallback".

Next, pass that path to the plantumlconfig attribute in your AsciiDoc document (or set the attribute via the CLI or API):

:plantumlconfig: plantuml.cfg

Clear the cache of your diagrams and run Asciidoctor PDF with Asciidoctor Diagram enabled. The diagrams will be generated using Noto Serif as the default font, and Asciidoctor PDF will know what to do.

The bottom line is this: If you’re using fonts in your SVG, and you want those fonts to be preserved, those fonts must be defined in the Asciidoctor PDF theme file.

Supporting Additional Image File Formats

In order to embed an image into a PDF, Asciidoctor PDF must understand how to read it. To perform this work, Asciidoctor delegates to the underlying libraries. Prawn provides support for reading JPG and PNG images. prawn-svg brings support for SVG images. Without any additional libraries, those are the only supported image file formats.

If you need support for additional image formats, such as GIF, TIFF, or interlaced PNG—and you don’t want to convert those images to a supported format—you must install the prawn-gmagick (>= 0.0.9) Ruby gem. prawn-gmagick is an extension for Prawn based on GraphicsMagick that adds support for all the image formats recognized by that library. prawn-gmagick has the added benefit of significantly reducing the time it takes to generate a PDF containing a lot of images.

The prawn-gmagick gem uses native extensions to compile against GraphicsMagick. This system prerequisite limits installation to Linux and OSX. Please refer to the README for prawn-gmagick to learn how to install it.

Once this gem is installed, Asciidoctor automatically switches over to it to handle embedding of all images. In addition to support for more additional image file formats, this gem also speeds up image processing considerably, so we highly recommend using it if you can.

STEM Support

Unlike the built-in HTML converter, Asciidoctor PDF does not provide native support for STEM blocks and inline macros (i.e., asciimath and latexmath). That’s because Asciidoctor core doesn’t process the STEM content itself. It just passes it through to the converter. In the HTML output, Asciidoctor relies on the JavaScript-based MathJax library to parse and render the equations in the browser when the page is loaded. The HTML converter simply wraps the equations in special markup so MathJax can find them.

In order to insert a rendered equation into the PDF, the toolchain has to parse the equations and convert them to a format the PDF writer (Prawn) can understand. That typically means converting to an image.

The recommended solution is an extension named Asciidoctor Mathematical, which we’ll cover in this document.

Another solution, which is still under development, uses Mathoid to convert STEM equations to images. Mathoid is a library that invokes MathJax using a headless browser, so it supports both asciimath and latexmath equations. That prototype can be found in the Asciidoctor extensions lab.

Asciidoctor Mathematical

Asciidoctor Mathematical is an extension for Asciidoctor that provides alternate processing of STEM blocks and inline macros (currently only latexmath). After the document has been parsed, the extension locates all the latexmath blocks and inline macros, converts the equations to images using Mathematical, then replaces them with image nodes. Conversion then proceeds as normal.

Asciidoctor Mathematical is a Ruby gem that uses native extensions. It has a few system prerequisites which limit installation to Linux and OSX. Please refer to the installation section in the Asciidoctor Mathematical README to learn how to install it.

Once Asciidoctor Mathematical is installed, you just need to enable it when invoking Asciidoctor PDF using the -r flag:

$ asciidoctor-pdf -r asciidoctor-mathematical sample.adoc

If you’re invoking Asciidoctor via the API, all you need to do is require the gem before invoking Asciidoctor:

require 'asciidoctor-mathematical'

Asciidoctor.convert_file 'sample.adoc', safe: :safe

To get the best quality equations, and the maximize speed of conversion, we recommend configuring Asciidoctor Mathematical to convert equations to SVG. You control this setting using the mathematical-format AsciiDoc attribute:

$ asciidoctor-pdf -r asciidoctor-mathematical -a mathematical-format=svg sample.adoc

Refer to the README for Asciidoctor Mathematical to learn about additional settings and options.

Skipping Passthrough Content

Asciidoctor PDF does not support arbitrary passthrough content. While the basebackend for the PDF converter is html, it only recognizes a limited subset of inline HTML elements that can be mapped to PDF (e.g., a, strong, em, code, ). Therefore, if your content contains passthrough blocks or inlines, you most likely have to use a conditional preprocessor to skip them (and make other arrangements).

Here’s an example of how to skip a passthrough block when converting to PDF:

ifndef::backend-pdf[]
<script>
//...
</script>
endif::[]

Here’s an example of how to only enable a passthrough block when convertering to HTML5:

ifdef::backend-html5[]
<script>
//...
</script>
endif::[]

Shaded Blocks and Performance

Certain blocks are rendered with a shaded background, such as verbatim (listing, literal, and source), sidebar, and example blocks. In order to calculate the dimensions of the shaded region, Asciidoctor PDF has to “dry run” the block to determine how many pages it consumes. While this strategy has a low impact when processing shorter blocks, it can drastically deteriorate performance when processing a block that spans dozens of pages. As a general rule of thumb, you should avoid using shaded blocks which span more than a handful of pages.

Autofitting Text

Verbatim blocks often have long lines that don’t fit within the fixed width of the PDF canvas. And unlike on the web, the PDF reader cannot scroll horizontally to reveal the overflow text. Therefore, the long lines are forced to wrap. Wrapped lines can make the verbatim blocks hard to read or even cause confusion.

To help address this problem, Asciidoctor PDF provides the autofit option on all verbatim (i.e., literal, listing and source) blocks to attempt to fit the text within the available width. When the autofit option is enabled, Asciidoctor PDF will decrease the font size until the longest line fits without wrapping.

🔥	The font size will not be decreased beyond the value of the `base_font_size_min` key specified in the PDF theme. If that threshold is reached, lines may still wrap.

Here’s an example of the autofit option enabled on a source block:

[source%autofit,java]
----
@SessionScoped
public class WidgetRepository {
    @GET
    @Produces("application/json")
    public List<String> listAll(@QueryParam("start") Integer start, @QueryParam("max") Integer max) {
        ...
    }
}
----

If you want to enable the autofit option globally, set the autofit-option document attribute in the document header (or somewhere before the relevant blocks):

:autofit-option:

Printing Page Ranges

The print dialog doesn’t understand the page numbers labels (which appear in the running content). Instead, it only considers physical pages. Therefore, to print a range of pages as they are labeled in the document, you need to add the number of front matter pages (i.e., the non-numbered pages) to the page number range in the print dialog.

For example, if you only want to print the first 5 pages labeled with a page number (e.g., 1-5), and there are 2 pages before the page labeled as page 1, you need to add 2 to both numbers in the range, giving you a physical page range of 3-7. That’s the range you need to enter into the print dialog.

Title Page

Unlike other converters, the PDF converter introduces a dedicated title page at the start of the document. The title page contains the doctitle, author, date, and revision info. If a front cover image is specified, the title page comes after the front cover. The title page can be styled using the theme and/or reserved page attributes.

The title page is enabled if either of these conditions are met:

The document has the book doctype.
The title-page attribute is set (with an empty value) in the document header.

When the title page is enabled, the table of contents (aka TOC) also gets is own page (or pages, if necessary).

The table of contents (TOC) is not included by default. The TOC is only included if the toc attribute is set on the document.

The placement of the table of contents is fixed, and thus the value of the toc attribute is effectively ignored in this backend. For documents that have the book doctype, the TOC is inserted using discrete pages between the title page and the first page of content. For all other doctypes (unless the title-page attribute is set), the TOC is inserted in the flow of text in between the document title and the first block of content.

While the table of contents is not included by default, the PDF outline is always included. The toclevels attribute controls the depth of both the TOC and the PDF outline (regardless of whether the TOC is enabled).

📎	If a document that has the book doctype includes a preface, an entry for the preface is only included in the TOC if the `preface-title` is assigned a value (e.g., `preface-title=Preface`). This value is used as the heading of the preface and as the text of the entry in the TOC.

Index Catalog

Asciidoctor PDF supports generating an index catalog that itemizes all index terms defined in the document, allowing the reader to navigate the document by keyword.

To get Asciidoctor PDF to generate an index, simply add an level-1 section flagged with the index style near the end of your document. The converter will automatically populate the catalog with the list of index terms in the document, organized by first letter.

[index]
= Index

You can use any text you want for the title of the section. The only restriction is that no index terms may be defined below this section.

📎	Although the catalog is generated automatically, you have to mark the index terms manually. However, you could use an extension, such as a TreeProcessor, to automatically mark index terms.

Optimizing the Generated PDF

optimize-pdf

Asciidoctor PDF also provides a shell script that uses GhostScript (gs) to optimize and compress the generated PDF (with minimal impact on quality). You must have Ghostscript installed to use it.

Here’s an example usage:

$ ./bin/optimize-pdf basic-example.pdf

The command will generate the file basic-example-optimized.pdf in the same directory.

⚠️	The `optimize-pdf` script currently requires a Bash shell (Linux, OSX, etc). We plan to rewrite the script in Ruby so it works across platforms (see issue #1)

If a file is found with the extension .pdfmark and the same rootname as the input file, it is used to add metadata to the generated PDF document. This file is necessary to preserve the document metadata since Ghostscript will otherwise drop it. That’s why Asciidoctor PDF always creates this file in addition to the PDF.

❗	The `optimize-pdf` script relies on Ghostscript >= 9.10. Otherwise, it may actually make the PDF larger. You should probably only consider using it if the file size of the original PDF is > 5MB.

hexapdf

Another option to optimize the PDF is hexapdf (gem: hexapdf, command: hexapdf). Before introducing it, though, it’s important to point out that its license is AGPL. If that’s okay with you, read on to learn how to use it.

First, install the hexapdf gem using the following command:

$ gem install hexapdf

You can then use it to optimize your PDF as follows:

$ hexapdf optimize --compress-pages --force basic-example.pdf basic-example-optimized.pdf

This command does not manipulate the images in any way. It merely compresses the objects in the PDF and prunes any unreachable references. But given how much waste Prawn leaves behind, this turns out to reduce the file size significantly.

To see more options, run:

$ hexapdf help optimize

For example, to make the source of the PDF a bit more readable, set the stream-related options to preserve.

hexapdf also allows you to add password protection to your PDF, if that’s something you’re interested in doing.

Contributing

In the spirit of free software, everyone is encouraged to help improve this project.

To contribute code, simply fork the project on GitHub, hack away and send a pull request with your proposed changes. All pull requests must include a) tests that verify the code change and b) an entry in the CHANGELOG.adoc file to document what changed. If a pull request is missing tests or a CHANGELOG entry, it will not be merged.

Feel free to use the issue tracker or Asciidoctor mailing list to provide feedback or suggestions in other ways.

Development

To help develop Asciidoctor PDF, or to simply use the development version, you need to get the source from GitHub. Follow the instructions below to learn how to clone the source and run it from your local copy.

Retrieve the Source Code

You can retrieve the source of Asciidoctor PDF in one of two ways:

Clone the git repository
Download a zip archive of the repository

Option 1: Fetch Using Git

If you want to clone the git repository, simply copy the GitHub repository URL and pass it to the git clone command:

$ git clone https://github.com/asciidoctor/asciidoctor-pdf

Next, change to the project directory:

$ cd asciidoctor-pdf

Option 2: Download the Archive

If you want to download a zip archive, click the Download Zip button on the right-hand side of the repository page on GitHub. Once the download finishes, extract the archive, open a console and change to that directory.

💡	Instead of working out of the asciidoctor-pdf directory, you can simply add the absolute path of the bin directory to your `PATH` environment variable.

We’ll leverage the project configuration to install the necessary dependencies.

Install Dependencies

If you’re using RVM, we recommend creating a new gemset to work with Asciidoctor PDF:

$ rvm use 2.5@asciidoctor-pdf --create

We like RVM because it keeps the dependencies required by various projects isolated.

The dependencies needed to use Asciidoctor PDF are defined in the Gemfile at the root of the project. We can use Bundler to install the dependencies for us.

To check you have Bundler available, use the bundle command to query the installed version:

$ bundle --version

If it’s not installed, use the gem command to install it.

$ gem install bundler

Then use the bundle command to install the project dependencies:

$ bundle

📎	You need to call `bundle` from the project directory so that it can find the Gemfile.

Run the Tests

Tests are written using RSpec. To run the tests, simply invoke rspec via bundler.

$ bundle exec rspec

To disable the visual integration tests, pass the `` option:

$ bundle exec rspec -t ~integration

If a visual integration test fails, you can instruct the test suite to keep the files in the spec/output directory by setting the DEBUG environment variable:

$ DEBUG=true bundle exec rspec -t integration

If you want to see the name of each test as it is run, add the -fd option:

$ bundle exec rspec -fd

You can also use the provided Rake task (note the name difference):

$ bundle exec rake spec

Running tests using rspec directly gives you the advantage of being able to specify additional options.

To run a single test, you can filter by the name of the test. For example, to run all tests that pertain to failures, use:

$ bundle exec rspec -e fail

To run all tests that have wip in the name, use:

$ bundle exec rspec -e wip

You can also run all tests in a given file by passing the file’s path to rspec:

$ bundle exec rspec spec/toc_spec.rb

For a full list of options that rspec provides, run rspec -h.

Run the Application (optional)

Like with Bundler, you have to run the application from the project directory. Assuming all the required gems install properly, verify you can run the asciidoctor-pdf script using Ruby:

$ bundle exec asciidoctor-pdf -v

If you see the version of Asciidoctor PDF printed, you’re ready to use Asciidoctor PDF!

You can use the application to convert a document as follows:

$ bundle exec asciidoctor-pdf /path/to/sample.adoc

Install the Application (optional)

If you want to install the application globally so you can run it anywhere, use the following rake task:

$ bundle exec rake install

This task will package the gem and install it into your system gems.

If you want to install the gem using a separate command, first use the following rake task to build it:

$ rm -rf pkg
  bundle exec rake build

This task packages the application as a gem and writes it to the pkg directory. A message will be printed to the console telling you the exact filename. You can now use the gem install command to install it.

$ gem install pkg/*.gem

You’ll want to pay attention to which Ruby installation you are installing the gem into. If successful, the asciidoctor-pdf executable will be available on your PATH.

Test a Pull Request

To test a pull request (PR), you first need to fetch the branch that contains the change and switch to it. The steps below are covered in detail in the GitHub help.

Let’s assume you want to test PR 955. Here’s how you fetch and switch to it:

$ git fetch origin pull/955/head:pr-955-review
  git checkout pr-955-review

❗	Make sure you replace the number with the number of the PR you want to test.

In case any dependencies have changed, you should run the bundle command again:

$ bundle

Now you can run the application as modified by the PR:

$ bundle exec asciidoctor-pdf /path/to/sample.adoc

To switch back to master, just type:

$ git checkout master

Resources

Discussion about image quality in PDFs

Authors

Asciidoctor PDF was written by Dan Allen and Sarah White of OpenDevise Inc. on behalf of the Asciidoctor Project.

Copyright

For the full text of the license, see the LICENSE file. Refer to the NOTICE file for information about third-party Open Source software in use.

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