If you work with accessible PDFs, you'll meet two standards constantly: WCAG and PDF/UA. They're often used interchangeably, but they're not the same thing — and understanding the difference is the key to getting compliance right.
WCAG: the "what" — content-level accessibility
WCAG (Web Content Accessibility Guidelines) defines what makes content accessible, organized around four principles: content must be perceivable, operable, understandable, and robust. It applies to web pages, apps, and documents published on the web. The conformance levels are A, AA, and AAA, with Level AA the target for nearly every compliance regime. WCAG is technology-neutral — it doesn't tell you how to build a PDF, it tells you the outcomes a PDF must achieve (sufficient contrast, meaningful link text, readable structure). Learn what changed recently in our WCAG 2.2 guide.
PDF/UA: the "how" — document-structure accessibility
PDF/UA-1 (ISO 14289-1) is PDF-specific. It defines how the PDF's internal structure must be built: a complete tag tree, correct reading order, a document title and language, properly tagged figures with alt text, and marked-up tables and forms. Where WCAG says "content must be navigable," PDF/UA says "the tag tree must contain these elements in this order." Because it's concrete and machine-testable, PDF/UA-1 is what validators like veraPDF check against. See our PDF/UA beginner's guide.
How they relate
They're complementary, not competing. For a PDF, WCAG 2.1 AA sets the goal; PDF/UA-1 is the technical way to get there at the document layer. A PDF/UA-valid document satisfies the structural WCAG requirements (reading order, structure, text alternatives). Content-level WCAG items — contrast, plain language, meaningful link text — still need attention, but those are judgment calls a validator can't fully check. That's why a clean validation report means "structurally sound," not "fully WCAG-reviewed." See how to read the report.
Which one does your compliance regime require?
Most cite WCAG 2.1 Level AA as the standard — ADA Title II, Section 508, the EU EAA. In practice, for PDF documents, that means building to PDF/UA-1 (the machine-checkable layer) plus reviewing WCAG content items. You don't choose between them; you meet WCAG by implementing PDF/UA. See our overview of PDF accessibility laws worldwide.
WCAG 2.1 vs 2.2
WCAG 2.2 AA is a superset of 2.1 AA — it adds nine success criteria, most about mobile and cognitive accessibility. The DOJ ADA Title II rule specifies 2.1 AA; conforming to 2.2 AA is a safe superset and future-proofs you. PDF/UA-1 remains the document-layer standard either way.
Check where you stand
Run your PDF through the free checker for the PDF/UA-1 layer, then review the content-level WCAG items manually. Our compliance checklist walks through both.
Sources and references
Practical compliance: what you actually do for each standard
The distinction between WCAG and PDF/UA is most useful when you are building a compliance workflow — not when you are reading about it. Here is what you do for each, in practice:
For the PDF/UA-1 layer (machine-checkable)
- Run the PDF through a PDF/UA-1 validator. This produces an objective failure list — you do not interpret or judge; the machine reports what is missing.
- Fix every failure the validator reports. Because the rules are deterministic, automated remediation handles the majority: tag tree, metadata, reading order, figure tagging.
- Re-validate after remediation. If the report is clean, the document is structurally compliant — the tag tree is complete, metadata is set, and the structure meets PDF/UA-1.
- Save the report. It is your compliance evidence for the document-structure layer.
For the WCAG content layer (judgment items)
- Review contrast: do text and backgrounds have sufficient contrast? This is a manual check — validators do not measure contrast in PDFs reliably.
- Review link text: are hyperlinks described meaningfully, or do they say "click here" or show raw URLs? Screen readers can navigate by link — each link should be understandable out of context.
- Review alt-text quality: does each description convey the information the image adds? This is the human-review item that automated tools flag but cannot judge.
- Review language and reading level: is the document written in clear, plain language appropriate for its audience? This is a WCAG AAA guideline (3.1.5) but good practice at any level.
What passes the audit
For most compliance regimes (ADA Title II, Section 508, EAA), the standard of evidence is: a clean PDF/UA-1 validation report plus a documented manual review of WCAG content items. Neither check alone is sufficient, but together they address both layers. See our compliance checklist for the combined workflow.