12 min read 22 October 2026

PDF Accessibility Testing Tools: PAC, veraPDF, axesPDF, and Screen Readers Compared

Automated PDF accessibility testing catches many structural failures — but not all. This guide compares PAC 2024, veraPDF, axesPDF, CommonLook, and manual screen reader testing, explaining what each tool checks, what it misses, and how to build a complete testing workflow.

Testing a PDF for accessibility requires more than running a single automated checker. Automated tools can verify that required structural elements are present — but they cannot judge whether a reading order makes logical sense, whether an image's alt text is actually informative, or whether a screen reader user can complete a form task. True accessibility testing combines automated structural checking with manual verification and real assistive technology testing. This guide covers the four main automated PDF accessibility tools used in 2024 — PAC 2024, veraPDF, axesPDF, and CommonLook — explaining what each checks, where each excels, what each misses, and how to build a testing workflow that catches both structural failures and real-world usability issues.

PAC 2024 — the gold standard for PDF/UA checking

PAC (PDF Accessibility Checker) is developed by Access For All and is free for Windows. PAC 2024 is the most widely referenced tool for PDF/UA conformance checking in European accessibility compliance contexts (EAA, EN 301 549). What PAC checks: PAC runs the Matterhorn Protocol test suite — the official PDF/UA-1 and (in 2024 and later) PDF/UA-2 checkpoint framework. It checks structural requirements: tagged content, reading order structure, heading hierarchy, table header associations, figure alt text, link text, form field labels, artifact marking, language declaration, and more. PAC's Screen Reader Preview is a distinguishing feature: it visualises the document's logical structure as a screen reader would encounter it, showing the tag tree in reading order. This is invaluable for manually inspecting reading order issues that automated checks cannot detect. PAC limitations: Windows-only; cannot batch-process large document sets; does not validate PDF/A conformance; the alt text quality check only verifies that alt text is present, not that it is meaningful. PAC 2024 for PDF/UA-2: Updated Matterhorn Protocol 2.0 checkpoints include /Aside, /FENote, and MathML validation. Validator updates may lag behind the standard — check the Access For All website for the current PAC version's conformance scope.

veraPDF — batch validation and PDF/A + PDF/UA

veraPDF is the open-source, industry-supported PDF validator developed under the PDF Association with funding from the EU's PREFORMA project. It is the reference validator for PDF/A conformance and includes PDF/UA-1 validation rules. What veraPDF checks: PDF/A-1a/1b, PDF/A-2a/2b/2u, PDF/A-3a/3b/3u, PDF/A-4, PDF/UA-1. For PDF/A, veraPDF is comprehensive and authoritative. For PDF/UA, veraPDF checks structural requirements but its PDF/UA ruleset is less exhaustive than PAC's Matterhorn Protocol implementation. veraPDF's strengths: Cross-platform (Java-based); command-line and GUI; batch processing of thousands of files; machine-readable XML/JSON reports; open policy configuration; CI/CD integration for automated compliance gating. For production document validation pipelines, veraPDF is the standard choice. veraPDF limitations: No screen reader preview; no visual rendering; PDF/UA coverage is less complete than PAC; requires Java runtime. Recommended combination: Use veraPDF for batch PDF/A validation and initial PDF/UA structural screening; use PAC for detailed Matterhorn Protocol checking and screen reader preview on representative samples.

axesPDF, CommonLook, and commercial tools

Several commercial tools address gaps left by PAC and veraPDF: axesPDF QuickFix — Windows-based tool developed by axes4. Combines automated checking with a guided remediation workflow inside Acrobat Pro. Its strength is the linked checker-and-fixer interface: failures are listed with direct links to jump to and fix each issue in the tag tree. Particularly useful for manual remediation workflows. CommonLook PDF GlobalAccess — A Acrobat Pro plugin by Netcentric Technologies. Provides HHS (US Section 508) and PDF/UA-1 checking with a step-by-step guided remediation process. Widely used in US federal government accessibility compliance workflows. Acrobat Pro's built-in Accessibility Checker — The "Accessibility Check" in Acrobat Pro (Tools > Accessibility > Accessibility Check) checks for common issues but has a different and less comprehensive ruleset than PAC or veraPDF. It is useful as a quick first pass but should not be relied on as the sole accessibility verification. Climbing to 100%: No automated tool catches all accessibility failures. The hardest failures to catch automatically: - Reading order correctness (the structural reading order must match the visual/logical order) - Alt text quality (present vs meaningful) - Table complexity (nested headers, irregular spans) - Form field usability (field purpose, error identification) Manual testing with JAWS, NVDA, or VoiceOver on representative document types is necessary for genuine accessibility assurance. See How to Audit a PDF for Accessibility for a complete workflow.

Frequently asked questions

Is it sufficient to pass PAC to be PDF/UA compliant?

PAC passing the Matterhorn Protocol automated checks is a necessary but not sufficient condition for PDF/UA compliance. The Matterhorn Protocol distinguishes between "machine-verifiable" checkpoints (which PAC can check automatically) and "human-verifiable" checkpoints (which require manual review). Human-verifiable items include: whether alt text is actually meaningful, whether heading structure reflects the logical document outline, whether reading order reflects the intended sequence, and whether form field labels convey the field's purpose. PDF/UA compliance requires all checkpoints — automated and human — to pass. A document can pass PAC's automated checks and still be effectively inaccessible if the human-verifiable items fail.

What is the difference between PDF/UA-1 and PDF/UA-2 checking?

PDF/UA-1 (ISO 14289-1:2014) and PDF/UA-2 (ISO 14289-2:2024) have overlapping but distinct requirements. Key PDF/UA-2 additions that checkers must cover: the /B role is no longer permitted for bold text (structure element /Strong must be used); new structure elements /Aside and /FENote have specific usage rules; MathML is the normative mechanism for mathematical content (not alt text approximations); /Artifact sub-types are extended. The Matterhorn Protocol was updated with new checkpoints for PDF/UA-2. PAC 2024 includes these new checkpoints; earlier PAC versions and veraPDF's PDF/UA ruleset may not cover all PDF/UA-2 checkpoints. When testing for PDF/UA-2 compliance, verify the tool's stated conformance scope.

How do I test PDF accessibility with a screen reader?

Manual screen reader testing is the most reliable way to evaluate real-world accessibility. The standard approach: (1) Use NVDA (free, Windows) or JAWS (commercial, Windows) with Adobe Acrobat Reader, or VoiceOver (built-in, macOS) with Preview or Safari. (2) Navigate the document using only keyboard commands — arrow keys, Tab for interactive elements, reading shortcuts. (3) Check: does the reading order match the visual order? Are headings announced at correct levels? Are images described? Are table headers read before cell values? Can form fields be completed with announced labels and instructions? (4) Specifically test any interactive elements (forms, links, media). Avoid testing only with Acrobat's built-in accessibility checker results as your proxy — use a real screen reader with real navigation.

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