How Do I Make a Scanned PDF Accessible?

A scanned PDF is just an image. It contains no actual text — which means a screen reader cannot read it at all. To someone using assistive technology, a scanned PDF is a blank page. To make it accessible, you need to run OCR (Optical Character Recognition) to extract the text from the image, and then add structure tags, reading order, alt text for figures, and other accessibility features. This is a two-step process: first make the content readable, then make it structured.

If you have old exams, photocopied handouts, or legacy documents sitting in a shared drive, chances are many of them are scanned PDFs. This guide walks you through exactly what to do with them.

Why Scanned PDFs Are the Worst Case for Accessibility

Most PDFs have at least some digital text in them, even if the structure is missing. A scanned PDF has nothing. It is literally a photograph of a page wrapped in a PDF container.

That means:

• Screen readers see an empty document. There is no text layer to read aloud.
• Users cannot select, copy, or search the text. It is locked inside an image.
• There is zero structure. No headings, no lists, no tables — just pixels.
• Zooming degrades quality. Users with low vision who enlarge the page get a blurry image instead of crisp, reflowable text.

A scanned PDF fails every WCAG 2.1 success criterion related to text content. It is the hardest type of document to remediate because you are starting from nothing.

Step 1: Run OCR to Extract the Text

OCR — Optical Character Recognition — is software that analyzes images of text and converts them into actual, selectable, machine-readable text. Think of it as teaching a computer to read a photograph of a page.

Modern OCR engines are remarkably accurate with printed text. When you run OCR on a scanned PDF, the software creates an invisible text layer behind the image, so the document looks the same visually but now contains real text that screen readers and search tools can access.

OCR Quality Depends on Scan Quality

Not all scans produce good OCR results. Here is what matters:

• Resolution: 300 DPI is the minimum for reliable OCR. Documents scanned at 150 DPI or lower will have significantly more errors. If you are scanning new documents, always use 300 DPI or higher.
• Contrast: Black text on a white background produces the best results. Faded text, colored backgrounds, or low-contrast combinations cause errors.
• Alignment: Skewed or rotated pages reduce accuracy. Most OCR tools can auto-correct minor skew, but heavily crooked scans will have problems.
• Handwriting: OCR is unreliable for handwritten text. If your scanned document contains handwriting, expect errors or unreadable output. Handwritten documents may need to be re-created rather than remediated.
• Clean copies: Smudges, coffee stains, hole-punch shadows, and margin notes all interfere with OCR. The cleaner the scan, the better the result.

How to Run OCR in Adobe Acrobat Pro

If you have Adobe Acrobat Pro, you can run OCR on a scanned PDF:

1. Open the scanned PDF in Acrobat Pro.
2. Go to Tools and select Scan & OCR.
3. Click Recognize Text and choose In This File.
4. Under Settings, set the language to match your document and choose Searchable Image as the output style.
5. Click Recognize Text and wait for processing to complete.
6. Save the file.

After this process, your PDF will have a text layer behind the scanned image. You can verify it worked by trying to select text on the page — if you can highlight words, OCR was successful.

Important: OCR Alone Is Not Enough

Running OCR gives you readable text, but it does not give you an accessible document. After OCR, your PDF still lacks:

• Heading structure — the document has no H1, H2, or H3 tags
• Reading order — assistive technology may read content in the wrong sequence
• Table markup — any tables are just text floating in space
• Alt text — images and figures have no descriptions
• List structure — bulleted or numbered lists are not tagged as lists
• Language metadata — the document may not declare its language

To complete the job, you need to add PDF tags and structure. For a full walkthrough of the tagging and remediation process, see our guide on how to make a PDF accessible.

Step 2: Add Structure and Tags

Once OCR has created the text layer, you need to tag the document — marking headings, paragraphs, tables, lists, images, and reading order. In Adobe Acrobat Pro, this is done through the Accessibility tools and the Tags panel.

This step is where most of the time goes. For a simple one-page handout, it might take 15 to 20 minutes. For a complex multi-page document with tables and figures, expect 45 to 90 minutes of manual work.

After tagging, run an accessibility check to verify your work. Our guide on how to check PDF accessibility covers the full process.

The Better Approach: Avoid Scanned PDFs When Possible

Before you spend an hour remediating a scanned PDF, ask yourself two questions:

Does the original digital file exist? Many scanned documents were originally created in Word, PowerPoint, or another application. If you can find the original file, it is almost always faster to export a fresh, accessible PDF from the source than to remediate the scan. Check with the original author, department archives, or shared drives.

Would it be faster to re-create the document? For short documents — a one-page syllabus policy, a half-page handout — it may take less time to retype the content in Word and export an accessible PDF than to run OCR, fix errors, and add tags to the scan.

If you are scanning new documents going forward, always scan at 300 DPI or higher, use a flatbed scanner rather than a phone camera, and keep the originals digital whenever possible.

At Scale: Automation Is Essential

If you have a handful of scanned PDFs, the manual process described above is manageable. But universities often have hundreds or thousands of legacy scanned documents across course sites, departmental archives, and shared drives.

At 45 to 90 minutes per document, remediating 200 scanned PDFs manually would take 150 to 300 hours of staff time. That is not realistic for most departments, especially with the April 2026 ADA Title II compliance deadline approaching.

Automated tools can run OCR and structure tagging in a single pipeline, processing documents in minutes rather than hours. The key is finding a solution that handles both steps — text recognition and accessibility tagging — rather than just OCR alone.

Aelira runs OCR and full remediation in a single pipeline — upload a scanned PDF and get back an accessible, tagged document. You can learn more about how the automated pipeline works or see real processing time comparisons. Try it free.

Quick Reference

• Scanned PDFs are pure images — screen readers cannot read them at all.
• Run OCR first to create a text layer. Use 300 DPI scans for best results.
• OCR alone is not enough — you still need to add tags, headings, reading order, and alt text.
• Find the original file if possible — it is almost always faster than remediating a scan.
• Re-create short documents rather than spending an hour on a one-page scan.
• At scale, automate. Manual remediation of hundreds of scanned PDFs is not feasible.