Scanned PDFs and OCR: making image-only documents accessible

A scanned PDF is a photograph of a page. To a screen reader it contains nothing at all — no words, no headings, no table — just “graphic.” Governments, universities, courts and hospitals hold enormous archives of them: old minutes, signed forms, course readings, records.

How to tell if a PDF is scanned

• Try to select a word with the text cursor. If you can only draw a box around the whole page, it’s an image.
• Press Ctrl+F / Cmd+F and search for a word you can see. No results means no text.
• In Acrobat, Scan & OCR will offer to “Recognize Text” if the document has none.

What OCR does — and doesn’t do

Optical character recognition (OCR) converts the picture of text into machine-readable characters. In Acrobat Pro: Scan & OCR → Recognize Text → In This File.

OCR gives you text. It does not give you:

• Accuracy — recognition errors are common with poor scans, small fonts, handwriting, stamps and columns. “Ill” becomes “111”, “rn” becomes “m”. A screen reader reads the mistakes faithfully.
• Structure — headings, lists and tables still need to be tagged.
• Reading order — columns and sidebars still need ordering.
• Alt text — signatures, seals, photos and charts still need descriptions.

So OCR is step one of remediation, not the whole job.

The full process

1. Rescan if you can. 300 dpi, straight, high contrast. Better input means far fewer errors.
2. Run OCR with the correct language.
3. Proofread and correct the recognized text against the image — especially names, numbers, dates and amounts.
4. Tag and order the document as described in how to make an accessible PDF.
5. Describe images, signatures and handwritten notes.
6. Verify with PAC and a screen reader.

Handling a scanned archive

You probably don’t need to remediate every page. Under the ADA Title II rule, old documents that aren’t currently used to access services may be exempt, and properly archived content has its own exception. A practical approach:

1. Inventory and classify — what is it, how often is it accessed, is it still in use?
2. Remediate what people actually use: current forms, policies in force, course readings this semester.
3. Replace high-use content with accessible HTML where possible.
4. Archive properly what’s kept only for reference, and offer accessible versions on request quickly.

For large scanned collections, our PDF remediation service combines high-accuracy OCR with human correction and tagging, in prioritized batches.