public class CustomPrintManagerBase : GridPrintManager
{
    public CustomPrintManagerBase(SfDataGrid dataGrid) : base(dataGrid)
    {

}
//To Return proper cell for caption summary cells
    public override ContentControl GetPrintCaptionSummaryCell(object group, string mappingName)
    {
        var cell = base.GetPrintCaptionSummaryCell(group, mappingName);
        cell.HorizontalAlignment = HorizontalAlignment.Right;
        cell.HorizontalContentAlignment = HorizontalAlignment.Right;
        return cell;
}
}

//To assign the custom print manager to grid when print preview is initialized at run time.
dataGrid.PrintSettings.PrintManagerBase = new CustomPrintManagerBase(dataGrid);