PDF/UA

What the word means

A PDF is, underneath, a set of drawing orders. Put this word here, that word there. Nothing in it says which of those words is a title and which is a footnote.

Software that reads a page aloud therefore has to guess, and it guesses from the order things were drawn in. On a page in two columns that order is often wrong, and the reading jumps from one column to the other line by line. PDF/UA removes the guessing: the file itself says this is a heading, this is a paragraph, this is a table, and this is the order to read them in.

What it does on a real document

On a payslip, the file says here is the table of the month's lines, here are its column headings, and this figure belongs under that heading. Somebody who cannot see the page is told the heading before the figure, instead of hearing a bare number.

The same file says which language it is written in, so the voice pronounces it properly, and gives every picture a sentence describing what it shows. A picture that only decorates is marked as such, and is passed over in silence rather than announced.

Where it comes from, and why

Putting the structure inside the document is older than the rule: that is what a tagged PDF carries, and it arrived in the format in 2001. What was missing was a rule saying exactly what a document owes its reader, and something to check it against.

That rule is an international standard, numbered ISO 14289-1, and it is what PDF/UA-1 means. A second part, ISO 14289-2, followed in 2024, for PDF 2.0. The two letters stand for universal accessibility. Public bodies are the ones that ask for it: a public service has to be usable by everybody it serves.

See it on a finished document

A tagged, accessible document A tagged list whose column is a picture The rules behind this word, and the texts they are read from