PDF accessibility, in plain language

Accessible PDFs contain hidden labels, called tags, that say what each part of the page is: a heading, a paragraph, a list or a table. When some or all of the tags are missing, screen readers can't tell these parts apart.

Most of the document has its hidden labels (tags), but some text or images were left out. Screen readers may skip that content.

Headings should be marked as headings, and their levels should go in order: a main heading, then sub-headings under it, without skipping a level.

Bulleted and numbered lists need to be marked as lists, not just typed with dashes or numbers.

A data table needs its header cells marked, so each value can be matched with its row and column.

A screen reader reads the page in a set order, which can differ from the way a person reads it on screen.

The hidden labels (tags) have duplicate or empty pieces. For example, a paragraph may be wrapped inside another paragraph.

Pictures, charts and logos need a short written description, called alt text. A screen reader reads it out loud in place of the image.

Some text is a picture of words, such as a screenshot or scanned page, instead of real text.

This PDF is a picture of paper pages. It has no text a computer can read, so there is nothing for a screen reader to read aloud.

Some images don't record where they sit on the page. Tools use this to re-flow the page when it is zoomed in or read on a small screen.

The text color and the background color are too close, for example light gray on white. There isn't enough contrast between them.

Lines, icons, chart parts or form borders are too faint against their background.

Some information is shown only by color, such as red text for overdue items or a chart legend that matches by color alone.

Some text is so small that it becomes hard to read, even when zoomed in.

Rows of spaces, dots or dashes are used to line things up, like "Chapter 1.......5".

Every PDF should have a clear title saved in its properties, and should show that title instead of the file name when it opens.

The PDF doesn't say which language it is written in, such as English or Spanish.

Some words or passages are in a different language from the rest, such as a Spanish paragraph in an English document. They aren't marked as such.

The PDF relies on fonts installed on the reader's computer instead of carrying its own copy.

Some characters use a special font code, such as icons, arrows or check marks from a symbol font. A screen reader can't turn them into words.

PDFs carry hidden file information, such as the title and a note saying the file follows the PDF accessibility standard. That information is missing.

Link text like "click here" or a long web address doesn't tell the reader where the link leads.

Bookmarks are the clickable outline in the PDF's side panel. They let readers jump to each section.

Every box, checkbox or button in a fillable form needs a label that says what it is for, such as "First name".