To most people, a PDF is just something you open and read. But for someone using a screen reader, the exact same PDF can be completely unusable — and the problem is rarely the screen reader itself, it's whether the PDF was built with accessibility in mind.
Why some PDFs don't work with screen readers
A screen reader relies on a PDF's internal tag structure to know what's a heading, what's body text, and what's an image that needs a spoken description. If a PDF was generated by scanning a paper document (which is really just a stitched-together image), a screen reader can't detect any text content at all — it's effectively a blank page to the reader.
A few things that shape the accessibility experience
- Whether there's a text layer: a scanned PDF without OCR (optical character recognition) has nothing for a screen reader to read aloud.
- Whether reading order is correct: multi-column layouts (like a newspaper) can trip up a screen reader if the tags are ordered wrong, reading text across columns in a confusing jumble.
- Whether images have alt text: an image with no alt text just gets announced as "image," leaving the user with no idea what it shows.
- Whether tables have header tags: a table without properly tagged headers can't tell a screen reader which row or column a given cell belongs to.
What you can do as an everyday user
If you're producing a PDF for public distribution (a government notice, an annual report, course materials), it's worth exporting directly from a text-based source (Word, a web page) rather than printing and scanning; adding a short caption to important images; and avoiding color-only distinctions (like "red means done") since a screen reader can't announce color.
A related note when editing
When you add text or images to a PDF with a tool like LocalPDF, that new content is layered on visually — it's a different thing from a formal accessibility tag system. If your use case has strict accessibility compliance requirements (say, a government agency publishing a document), run it through a dedicated accessibility checker after editing.
Now that you know the basics, head back and try adding some text or images.
Open LocalPDF →