PDF/UA and WCAG get mentioned in the same sentence so often that many teams assume they are two names for one rule. They are two different documents with different jobs. WCAG is a set of success criteria from the W3C. PDF/UA is an ISO standard for how a PDF file must be built. A PDF can meet one and miss the other, and the contract or law you work under decides which one you have to show.
This guide explains what each standard covers, where they overlap, which one a US buyer usually needs, and what a PDF must contain to satisfy both.
What PDF/UA is
PDF/UA stands for PDF/Universal Accessibility. It is published as ISO 14289. Part 1, ISO 14289-1 (PDF/UA-1), covers PDF files built on the PDF 1.7 specification, and it has been the working reference for accessible PDFs for years. Part 2, ISO 14289-2 (PDF/UA-2), was published in 2024 and targets PDF 2.0. The PDF Association states that PDF/UA-2 does not replace PDF/UA-1. Most validators and most procurement language still point at PDF/UA-1.
The standard speaks to the file, not the reader. It lists what has to be true inside the PDF so that screen readers, magnifiers and other assistive technology can use it. The PDF Association turned those rules into the Matterhorn Protocol, which breaks PDF/UA-1 into 136 failure conditions grouped under 31 checkpoints. Some of those conditions a program can test alone. Others need a person to look.
If you are new to the vocabulary, our guides on what an accessible PDF is and what a tagged PDF is cover the basics. Every PDF/UA file is a tagged PDF, but a tagged PDF is not automatically PDF/UA.
What WCAG covers for PDF
WCAG, the Web Content Accessibility Guidelines, does not mention PDF in its success criteria. It is written to apply to any web content, and PDFs that are published on the web fall under it. The W3C supplies PDF techniques that show how to meet individual criteria in a PDF, such as adding alternative text to a figure or setting the document language.
WCAG judges outcomes. Can a person who cannot see the screen follow the document? Is the text readable against its background? Is the reading order meaningful? Is every form field named? These are questions about the experience, and some of them need human judgment, like whether alt text actually describes the image.
How the two overlap and where they differ
The overlap is large. Structure, reading order, alt text, document language, table headers, form field names and a document title appear in both. The PDF Association describes PDF/UA as complementing WCAG 2.0, and it publishes a comparison of the two that shows how much they share.
The differences show up at the edges. PDF/UA sets no contrast ratios and no rules for text size or the quality of your writing. WCAG says nothing about low-level file details such as how fonts are embedded and mapped to Unicode, or whether artifacts like page numbers are marked so they stay out of the tag tree. A PDF can pass a PDF/UA validator and still have pale gray text that fails WCAG contrast. Another PDF can read well to a person and still fail PDF/UA because a tag is malformed.
Side by side
| Question | PDF/UA (ISO 14289) | WCAG |
|---|---|---|
| Who publishes it | ISO, with the PDF Association | W3C |
| What it applies to | PDF files only | Any web content, including PDFs on the web |
| Style | Technical rules for file structure | Outcome-based success criteria |
| Current versions | PDF/UA-1 (PDF 1.7), PDF/UA-2 (PDF 2.0, 2024) | 2.0, 2.1 and 2.2 |
| Tags and reading order | Required, with strict rules on tag use | Required through structure and sequence criteria |
| Color contrast | No contrast ratios set | Covered |
| Quality of alt text | Requires that alt text exists | Requires that it serves the purpose of the image |
| How you prove it | Validator report against the Matterhorn Protocol, plus manual checks | Audit against each success criterion, usually with an ACR/VPAT |
| Named in law | Rarely | Often |
Which one a US buyer needs
US rules point at WCAG, not at PDF/UA.
- ADA Title II: the DOJ rule for state and local governments sets WCAG 2.1 Level AA, with compliance dates of 26 April 2027 for larger entities and 26 April 2028 for smaller ones. The rule covers web content and documents, which includes PDFs.
- Section 508: the refreshed standards incorporate WCAG 2.0 Level A and AA for electronic content, and that includes PDFs.
- European Accessibility Act: it relies on EN 301 549, which maps its web and document requirements to WCAG 2.1 AA.
PDF/UA enters through procurement. Federal agencies, universities, publishers and large enterprises often write "PDF/UA-1 conformance" into a request for proposal or a vendor contract because it gives them a test they can run on a file. Ask which standard the contract actually names. If it names WCAG, your evidence is a WCAG conformance statement. If it names PDF/UA, you need a validator result. When it names both, plan for both. This is an engineering view, not legal advice, and your counsel should confirm what applies to you.
What a PDF needs to pass both
The shared checklist is short enough to keep next to the file.
- Tags on all real content, with artifacts such as headers, footers and page numbers marked as artifacts.
- A reading order that matches the logical flow, including multi-column pages.
- Heading tags in order, with no jump from H1 to H4.
- Alt text on every meaningful image, and decorative images marked as artifacts.
- Table headers set, so a screen reader announces the column and row of each cell.
- Form fields with labels or tooltips and a sensible tab order.
- A document language, and language changes marked for passages in another language.
- A document title that displays in the title bar rather than the file name.
- Bookmarks for long documents.
- Text with enough contrast and real text rather than scanned images of text (WCAG side).
- Embedded fonts that map to Unicode so the text can be read out correctly (PDF/UA side).
Our PDF accessibility checklist walks through each item in the order you would fix it.
How to check a PDF against both
Run a PDF/UA validator first. It finds structural errors fast. PAC and veraPDF are two free validators that implement the Matterhorn Protocol, and Acrobat has its own checker with different rules, so expect the reports to disagree on some items. Then test the things a validator cannot judge: read the document with a screen reader, tab through the form, check contrast, and confirm that alt text means something.
If you want a first read without installing anything, the free PDF accessibility checker takes an uploaded PDF or a pasted URL and returns a score, the issues it found, and a time and cost estimate for fixing them. Our guide to checking a PDF for accessibility covers the manual steps.
Fixing the file instead of the report
A report tells you what is broken. The file still needs repair. WebAbility's PDF remediation fixes the real PDF, including tags and reading order, runs a PDF/UA check on the result, and adds an ACR/VPAT report you can hand to a buyer. Processing and preview are free. After you approve the preview, one credit covers up to 10 pages, with a minimum of one credit per document.
PDF/UA vs WCAG: common questions
Is PDF/UA the same as WCAG?
No. WCAG is a W3C set of success criteria for web content. PDF/UA is an ISO standard for the structure of PDF files. They share many requirements, but each has rules the other lacks.
Does a PDF/UA file meet WCAG?
Mostly for structure, not completely. PDF/UA sets no contrast ratios and does not judge your content, so a PDF/UA file can still fail WCAG criteria.
Is PDF/UA required in the United States?
Not by the main laws. ADA Title II names WCAG 2.1 AA and Section 508 names WCAG 2.0 AA. PDF/UA is requested in contracts and procurement, so check the document you are signing.
What is the difference between PDF/UA-1 and PDF/UA-2?
PDF/UA-1 (ISO 14289-1) applies to PDF 1.7 files. PDF/UA-2 (ISO 14289-2, 2024) applies to PDF 2.0. PDF/UA-2 does not replace PDF/UA-1, and PDF/UA-1 remains the version most tools test.
Can I check PDF/UA without Acrobat?
Yes. PAC and veraPDF are free validators, and the WebAbility checker gives a first score. Pair any of them with a manual screen reader check.
Which should I aim for?
Aim for the standard your contract or law names, and build the file so it meets both. The checklist above covers the shared ground, and the contrast and content checks cover what PDF/UA leaves out.
