How to Add Alt Text to Images in a PDF
Alternative text (alt text) is the short description a screen reader announces in place of an image. Without it, a screen reader either says nothing or reads the file name, and the user misses whatever the image conveys. Adding alt text is one of the highest-impact, lowest-effort accessibility fixes you can make.
Decide whether each image is meaningful or decorative
Before writing anything, decide what each image is for. If it carries information — a chart, a diagram, a photo that matters to the content — it needs alt text. If it is purely decorative — a border, a background flourish, a divider — it should be marked as an artifact so assistive technology skips it entirely.
Marking decorative images as artifacts is just as important as adding alt text. An accessible PDF should have no unexplained images.
How to add alt text in Acrobat Pro
- 1Open the PDF in Acrobat Pro and choose All tools > Prepare for accessibility.
- 2Select "Set alternate text". Acrobat steps through each image in turn.
- 3For meaningful images, type a concise description. For decorative ones, tick the "Decorative figure" box.
- 4Save the file and re-run the accessibility check to confirm no images are flagged.
What makes good alt text
- Be concise — one short sentence is usually enough.
- Describe the meaning, not the appearance. "Sales grew 30% from 2024 to 2025" beats "bar chart".
- Do not start with "image of" or "picture of" — the screen reader already announces it is a figure.
- For a complex chart, put the underlying data in the page text and keep the alt text a short summary.
- Do not duplicate a caption that already appears in the page text.
Text inside images
If an image contains text — a logo with a tagline, a screenshot of a document — that text must appear in the alt text, or better, as real text on the page. Otherwise it is invisible to screen readers and to search engines.
Run a free check on this site to see every image in your PDF that is still missing alternative text.