The PDF Problem

01Structure Is Not Decoration

A sighted reader looks at a page and reads a heading because it is large and bold, sitting above a block of smaller text. The visual cues are real and informative — but they live only in the eye. A screen reader, a refreshable display, a text-to-speech engine: none of these see a page. They need the structure to be declared explicitly, not performed visually.

The PDF format can carry that declaration. A tagged PDF embeds a logical tree alongside the visual layer: this span of text is a heading, this is a paragraph, this is a caption, this is decorative and should be skipped. A reading system can then navigate by heading, move between list items, and know the order in which content should flow — even when the visual layout arranges columns or sidebars that bear no relation to reading sequence.

Most PDFs carry none of this. A document exported from a word processor without accessibility settings produces a file that looks correct on screen and is, beneath the surface, a sequence of positioned drawing commands. A scanned page is worse: an image of text, not text at all. The letters are pixels. A screen reader finds the file and reads nothing, or reads a filename, and stops.

Optical character recognition can convert a scanned image to actual characters, but recognition alone does not produce structure. The output is a single undifferentiated string — no headings, no reading order, no indication of what is a column header and what is body copy. Structure must be added by hand, which means someone trained in PDF remediation working through a document element by element, tagging each one correctly, and checking the result with the tools a reader actually uses.

That work is slow and skilled. On a complex academic paper with figures, tables, equations and footnotes, it can take many hours. Publishers produce thousands of PDFs. The arithmetic explains why the catalogue of accessible titles is so thin: remediation is not being skipped out of carelessness, but because no one has yet built the cost of doing it into the ordinary price of making a document.