A scanned PDF is just that, a scanned image of a document that is saved as a PDF. Adobe also has an app called Adobe Scan that allows you to scan a document to PDF using your smart phone.
Scanned PDFs are missing tags. Tags provide screen readers with the coding to read the text in the PDF. People use screen readers for many different reasons including a visual impairment, cognitive disability and learning style preference.
The first thing to do after scanning a document to make it accessible (add tags) is to perform text recognition.
- Open the PDF in Adobe Acrobat Pro DC.
- Find and open the Enhance Scans tool.
- On the toolbar choose Enhance, Scanned Document.
- Ensure the Recognize Text box is checked and select Enhance.
- Open the Tags pane.
- Select the Tags menu and select Add Tags to Document.

Using the Enhance Scan tool improves the accuracy of text recognition. It enhances the quality of the scan prior to running Optical Character Recognition (OCR).
Now that the document is tagged, it is imperative to remediate accessibility issues to ensure it is fully accessible and usable.

This image shows that there are still some remediation issues to address after adding Tags to the document.
The final steps include:
- Running the Full Check in the Accessibility tool.
- Remediating the issues in the Accessibility Checker pane.
- Verify accuracy of all tags.
- Verifying the correct reading order.
- Verify accuracy of alternate text for images.
- Identify color/contrast issues
Creating an accessible PDF is not your only option for providing content on the web. Consider other options, such as creating a web page, before deciding on the PDF format.