feat: add PDF/UA (Universal Accessibility) support

[heikofolkerts]

Summary

This PR adds comprehensive PDF/UA (Universal Accessibility) support to jsPDF, enabling the creation of accessible PDF documents that comply with ISO 14289-1 (PDF/UA-1).

Key Features

• PDF/UA Mode: Enable with new jsPDF({ pdfUA: true })
• Structure Tree: Complete tagged PDF structure with proper hierarchy
• Document Metadata: XMP metadata with PDF/UA identification, document title, language
• Accessible Text: All text content is properly tagged and marked
• Embedded Fonts: Atkinson Hyperlegible font family (Regular, Bold, Italic, BoldItalic) with full Unicode support
• Images: Figure elements with alternative text support
• Tables: Proper table structure with TH/TD, row/column headers, and scope attributes
• Lists: Ordered and unordered lists with proper L/LI/Lbl/LBody structure
• Links: Accessible hyperlinks with OBJR references
• Semantic Elements: Strong, Em, Span, Quote, BlockQuote, Code, Note, Reference
• Advanced Features: TOC, Bookmarks, Artifacts, Form Fields, Abbreviations, Formula, BibEntry, Index, Ruby/Warichu annotations
• Multi-language: Language attributes at document and element level

New API Methods

// Enable PDF/UA mode
const doc = new jsPDF({ pdfUA: true });

// Document metadata
doc.setDocumentTitle('My Accessible Document');
doc.setLanguage('en-US');

// Structure elements
doc.beginStructureElement('H1');
doc.text('Heading', 20, 20);
doc.endStructureElement();

// Images with alt text
doc.addAccessibleImage(imageData, x, y, width, height, 'Alternative text');

// Tables with headers
doc.beginTableHeaderCell('Column');
doc.beginTableHeaderCell('Row');

// Lists
doc.beginList();
doc.beginListItem();
doc.addListLabel('•', x, y);
doc.beginListBody();
// ... content

Files Changed

• src/jspdf.js - PDF/UA initialization, font loading, API integration
• src/modules/structure_tree.js - Core structure tree implementation (new)
• src/modules/pdfua_fonts.js - Atkinson Hyperlegible font data (new)
• src/modules/xmp_metadata.js - Enhanced XMP metadata for PDF/UA
• src/modules/annotations.js - Link annotation support
• src/modules/acroform.js - Accessible form fields
• types/index.d.ts - Complete TypeScript definitions

Testing

• 525+ lines of unit tests in test/specs/pdfua.spec.js
• 35+ feature test suites in tests/pdfua/
• Comprehensive showcase document demonstrating all features
• Tested with:
  • PAC 2024 (PDF Accessibility Checker)
  • veraPDF validator
  • Adobe Acrobat Pro accessibility checker
  • Screen readers (NVDA, JAWS)

Documentation

Complete documentation in docs/pdfua/:

• API Reference
• Quick Start Guide
• Feature Examples
• Accessibility Best Practices

Backward Compatibility

• All existing jsPDF functionality remains unchanged
• PDF/UA features are opt-in via { pdfUA: true } option
• All existing tests pass (487 specs, 0 failures)

Test plan

• All existing unit tests pass
• New PDF/UA unit tests pass
• TypeScript compilation succeeds
• Generated PDFs validate with PAC 2024
• Generated PDFs validate with veraPDF
• Screen readers can navigate structure tree
• Build succeeds for all module formats (UMD, ES, CJS)

🤖 Generated with Claude Code

[heikofolkerts]

Hi maintainers,

I've just updated this PR to:

• Merge upstream/master (v4.0.0) to resolve merge conflicts
• Fix Prettier formatting issues that were causing lint check failures
• Rebuild dist files

All local tests pass (495 specs, 0 failures) and the Snyk security check has passed.

Could you please approve the CI workflow run so the full test suite can execute? The workflow is waiting for approval here:
https://github.com/MrRio/jsPDF/actions/runs/20431700538

Thank you!