PDF Accessibility Basics: Making Documents Usable for Everyone

A PDF that looks perfect on screen can be unusable for someone relying on a screen reader, a screen magnifier, or a keyboard instead of a mouse. PDF accessibility is the practice of structuring a document so assistive technology can actually parse it — not just display it.

Tagged PDFs: the foundation

A "tagged" PDF has an underlying structure tree that marks headings, paragraphs, lists, and tables as what they actually are — not just visually styled text. Without tags, a screen reader sees an undifferentiated wall of characters with no sense of hierarchy or reading order. Most PDFs exported directly from Word or Google Docs are tagged by default; PDFs created by "print to PDF" from a scanned image are not.

Reading order matters more than layout

Visually, a two-column layout reads top-to-bottom within each column. But the underlying content stream might store the text in a completely different order — a screen reader follows that stream, not the visual layout. This is the single most common accessibility failure in multi-column or design-heavy PDFs.

Alt text for images and charts

Any image that conveys information — a chart, a diagram, a screenshot with text in it — needs a text alternative describing what it shows. A decorative image (a divider line, a background pattern) doesn’t need alt text, but should be marked as an artifact so screen readers skip over it instead of announcing "image" with no context.

Color contrast is accessibility too

Low-contrast text — light gray on white, for example — fails accessibility guidelines (WCAG recommends a minimum 4.5:1 contrast ratio for normal text) even though it has nothing to do with screen readers. It affects anyone with low vision, older monitors, or simply a sunny room. It’s one of the easiest accessibility issues to catch with an automated audit, and one of the easiest to fix — a one-line color change, no structural rework required.

• Use a real heading structure (H1, H2, H3) instead of just making text bold and bigger.
• Add alt text to every image that conveys information.
• Check reading order in multi-column layouts before publishing.
• Verify text contrast meets at least 4.5:1 against its background.
• Avoid scanned-image-only PDFs for anything meant to be read by assistive technology — OCR first.