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Accessibility · PDF/UA

What is PDF/UA?

PDF/UA (ISO 14289) is the standard for PDFs that work with screen readers and assistive technology. Drop a file for a free structural scorecard — no signup.

ISO 14289 · PDF/UA-1 + PDF/UA-2 · validated by Preflight's Accessibility module (also WCAG 2.2, Section 508, EN 301 549).

Tagged content
Every piece of real content is tagged; decorative content is marked as an artifact, not tagged.
Reading order
The structure tree reflects the intended logical reading order, independent of visual layout.
Headings
A proper heading hierarchy with no skipped or misused levels.
Alt text
Figures and meaningful images carry alternative descriptions (decorative ones are artifacts).
Tables
Header cells, scope, and a regular row/column structure.
Language
A declared document language, plus per-span language changes.
Metadata
A document title that is set and shown, and the PDF/UA identification in XMP.
Mappable tags
Non-standard tags role-map to standard structure types.

PDF/UA (“Universal Accessibility”) specifies what a PDF needs to deliver a consistent, high-quality reading experience through assistive technology. The mechanism is tagged PDF: a logical structure tree that labels every piece of real content — headings, paragraphs, lists, tables, figures — in the correct reading order, with alternative text for images and a declared document language. Conformance is tested with the Matterhorn Protocol (31 checkpoints, 136 failure conditions; 87 software-checkable, 47 human-judgment).

How to make a PDF/UA-compliant file

  1. Start from a tagged source — author with real styles (headings, lists, tables) so structure exports as tags, not loose text.
  2. Set reading order and alt text — verify the tag tree matches the visual order and add alternative text to every meaningful image.
  3. Declare language and title — set the document language and a descriptive title, and show the title rather than the filename.
  4. Mark artifacts — tag decorative elements, running headers/footers, and backgrounds as artifacts so assistive tech skips them.
  5. Validate, then review by hand — run a machine check for the 87 automatable Matterhorn conditions, then have a person confirm the 47 that need human judgment.
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Frequently asked questions

Is PDF/UA the same as WCAG?

They are complementary. WCAG is the web-wide accessibility guideline; PDF/UA is the file-format standard that defines how a PDF meets those goals via tagged structure. Preflight checks both, plus Section 508 and EN 301 549.

What is tagged PDF?

A hidden logical structure tree that labels headings, paragraphs, lists, tables, and figures in reading order, so assistive technology can interpret the document correctly.

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

PDF/UA-1 (ISO 14289-1:2014) is based on PDF 1.7; PDF/UA-2 (ISO 14289-2:2024) is based on PDF 2.0 and aligns with modern well-tagged PDF practice. Preflight validates both.

What is the Matterhorn Protocol?

A free PDF Association testing model of 31 checkpoints and 136 failure conditions for PDF/UA; 87 are software-checkable and 47 require human review. Preflight automates the machine-checkable conditions and flags the rest rather than guessing.

Can a file be both PDF/A and PDF/UA?

Yes, and it is common for archiving — pair PDF/A-2 or A-3 with PDF/UA-1 (PDF 1.7), or PDF/A-4 with PDF/UA-2 (PDF 2.0). Preflight can validate each.

Related

What is PDF/UA? The PDF accessibility standard · Preflight