The first step in making scanned documents accessible is to perform Optical Character Recognition, or OCR, on the scanned page image. OCR converts images of alphanumeric characters into actual text that can be searched, read by assistive technology, exported to other formats or copied and pasted into other applications. Acrobat has an OCR text recognition feature that allows you to apply OCR to the scanned pages.
The resulting PDF files contain computer-generated text, which is necessary for making the file's information accessible to screen readers and other assistive technologies. You may need to further process the files at this point by using the accessibility authoring tools in Acrobat to add structure (tags), alternate text for graphics that appear in the file, and accessible form fields if applicable. You may also need to adjust the reading and tab order for interactive PDF file components. The Make Accessible Action in Acrobat Pro DC helps to automate many of these tasks.