I was running into the same errors as this issue and was particularly confused about this error:

Uncaught (in promise) TypeError: Cannot read property 'split' of undefined
    at new AFMFont (pdfkit.es5.js:2453)
    at new StandardFont (pdfkit.es5.js:2700)
    at Function.open (pdfkit.es5.js:3096)
    at PDFDocument.font (pdfkit.es5.js:3170)
    at PDFDocument.initFonts (pdfkit.es5.js:3132)
    at new PDFDocument (pdfkit.es5.js:4890)
    at new PDFBuilder (PDFBuilder.js:42)
    at PDFCreator.createID (index.jsx:40)
    at PDFCreator.componentDidMount (index.jsx:72)

The proposed workaround was to do a direct import from raw-loader:

import Helvetica from '!!raw-loader!pdfkit/js/data/Helvetica.afm'

This was strange to me as removing the !!raw-loader! portion still seemed to work and furthermore adding !!raw-loader! to the require.context call did not fix the error.

Turns out you just needed to use the default export of the files to avoid the error:

fs.writeFileSync(`data/${match[0]}`, ctx(key).default);

Not sure if this was a pdfkit update or what but it'd be good to update that line.

"pdfkit": "^0.10.0"
"webpack": "^4.39.2"
"arraybuffer-loader": "^1.0.7"
"raw-loader": "^3.1.0"
"transform-loader": "^0.2.4"

I've used your webpack example to extend my create-react-app setup.
I've added your rules to my webpack.config.js but there must a problem with the asset inlining.

in fact this does nothing in my generated webpack chunk:
{ loader: 'raw-loader', test: /\.afm$/ }

this is applied to the webpack output, which indicates that this a problem on the loader side and not a problem with your registerAFMFonts:

var map = {
	"./Helvetica.afm": "./node_modules/pdfkit/js/data/Helvetica.afm"
};

But when i double check the chunk contents there are no inlined glyphs.
That's a pity because i really appreciated the approach with kicking out all the unnecessary embedded fonts. In fact everything up the stack trace works well until the PDFDocument constructor tries to load the standard Helvetica font file, then the app crashes with an uncaught error...

The only thing i modified is the pattern which chooses the font variants. I only want the standard Helvetica to be inlined, like this:

registerAFMFonts(require.context('pdfkit/js/data', false, /Helvetica\.afm$/));

Here's the trace:

Uncaught (in promise) Error: File 'data/Helvetica.afm' not found in virtual file system
    at VirtualFileSystem.readFileSync (virtual-fs.js:22)
    at Object.Helvetica (pdfkit.es5.js:2658)
    at new StandardFont (pdfkit.es5.js:2700)
    at Function.open (pdfkit.es5.js:3096)
    at PDFDocument.font (pdfkit.es5.js:3170)
    at PDFDocument.initFonts (pdfkit.es5.js:3132)
    at new PDFDocument (pdfkit.es5.js:4890)
    at new PDFBuilder (PDFBuilder.js:42)
    at PDFCreator.createID (index.jsx:40)
    at PDFCreator.componentDidMount (index.jsx:72)

Any ideas how to ensure that the file will be inlined into the chunk or safely referenced in the virtual file system?
Cheers and thx in advance

just a little thing, iconv-lite was missing for me so I had to add it myself

getting this:

Error: Compiling RuleSet failed: Query arguments on 'loader' has been removed in favor of the 'options' property (at ruleSet[1].rules[5].loader: transform-loader?brfs)
    at RuleSetCompiler.error (/Users/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:365:10)
    at /Users/.../node_modules/webpack/lib/rules/UseEffectRulePlugin.js:160:29
    at Hook.eval [as call] (eval at create (/Users/.../node_modules/webpack/node_modules/tapable/lib/HookCodeFactory.js:19:10), <anonymous>:41:1)
    at RuleSetCompiler.compileRule (/Users/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:175:19)
    at /Users/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:152:9
    at Array.map (<anonymous>)
    at RuleSetCompiler.compileRules (/Users/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:151:16)
    at RuleSetCompiler.compileRule (/Users/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:182:30)
    at /Users/kelly/.../node_modules/webpack/lib/rules/RuleSetCompiler.js:152:9
    at Array.map (<anonymous>)

ERROR in ./node_modules/_fontkit@1.9.0@fontkit/dist/module.mjs 7463:26
Module parse failed: Unexpected token (7463:26)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
| };
| class $5340de7a86f3ae85$export$2e2bcd8739ae039 {

static zeroMarkWidths = 'AFTER_GPOS';

| static plan(plan, glyphs, features) {
| // Plan the features we want to apply
@ ./node_modules/_pdfkit@0.10.0@pdfkit/js/pdfkit.es5.js 5:0-30 3640:15-22 3642:15-22 3644:15-22
@ ./src/index.js

how can i solve this promble? i dont kown what error happend