Making PDFs Accessible: Tags, Structure, and Compliance

Screen readers parse PDF structure tags to determine reading order, heading hierarchy, and content relationships. Without proper tags, a screen reader reads the raw text stream in physical order — which may not match the visual reading order, especially in multi-column layouts, tables, and documents with sidebars.

Legal compliance is increasingly enforced. Section 508 requires federal agencies to produce accessible documents. The European Accessibility Act (2025) extends requirements to private sector websites and documents. Organizations that distribute inaccessible PDFs face legal risk and exclude a significant portion of their audience.

Document structure tags define headings (H1-H6), paragraphs (P), lists (L, LI), tables (Table, TR, TH, TD), and figures (Figure). These tags create a logical reading order independent of visual layout. Without them, a two-column layout reads straight across both columns instead of column-by-column.

Alternative text for images lets screen readers describe visual content. Every informational image needs a concise alt text describing what it conveys. Decorative images (borders, spacers) should be marked as artifacts so screen readers skip them entirely.

Form fields must have associated labels that screen readers can announce. A field labeled only by visual proximity (the label is next to the field but not programmatically linked) is invisible to assistive technology.

The most effective approach is to create accessible source documents. In Word, use built-in heading styles (Heading 1, Heading 2) instead of manually formatting text as bold and large. Use Word's table tools rather than tab-separated columns. Add alt text to all images via the image properties dialog.

When you convert Word to PDF, the heading structure, alt text, and table markup transfer into PDF structure tags automatically. The resulting PDF is accessible by default if the source document was properly structured.

Adobe Acrobat Pro's Accessibility Checker identifies common issues: missing tags, empty alt text, untagged tables, and reading order problems. The free PAC (PDF Accessibility Checker) tool provides a more thorough WCAG-based audit.

Manual testing with a screen reader (NVDA on Windows, VoiceOver on macOS) is essential. Automated checkers catch structural issues but cannot evaluate whether alt text is meaningful, whether reading order makes sense, or whether the document is actually usable with assistive technology.