How do I make a PDF accessible?

An accessible PDF needs a logical tag structure (headings, lists, tables), alt text for images, a defined reading order, a specified document language, sufficient color contrast, and labeled form fields — and it must be real selectable text, not a scanned image. Scanned documents have to go through OCR first to create a text layer before any tagging is possible. The most efficient approach is building accessibility into the source file — using heading styles and alt text in Word or InDesign, then exporting as a tagged PDF — rather than retrofitting an untagged PDF afterward. Section 508 and ADA Titles II and III all extend to PDFs, and they are increasingly cited in demand letters and lawsuits.