PDFs of scanned documents are often just images of documents, similar to digital photographs, and typically do not contain readable text. Unless the PDF is created as a text-based file or processed using Optical Character Recognition (OCR), screen readers and many other types of assistive technology cannot interpet the content.
Why Text-Based PDFs Matter
Text-based PDFs are essential for accessibility, assistive technologies like screen readers, text-to-speech software, enlargers, and others to interact with the content. Text-based PDFs also allow the user to adjust the text as needed, for example, changing size, color, font, etc. They also improve searchability, allowing search engines to index the document’s text. Simply printing a document to PDF or scanning without OCR usually results in an image-based, non-accessible file.
Optical Character Recognition (OCR)
OCR is a technology that converts printed or handwritten text in scanned documents into machine-readable text. When a document is scanned using OCR software, the system recognizes the characters and creates a digital version that can be read by assistive technology. Many modern scanners include OCR functionality—refer to your device's manual to confirm this feature.
Creating PDFs
Export from an accessible document
Whenever possible, create PDFs directly from other accessible formats. This will improve accessibility of your PDF document. Refer to the following guides:
Scan your document with OCR
If you are working with a hard copy, check first to see if an electronic version is available to download from JMU Libraries.
If not, use a scanner with OCR capabilities. Many new scanners have OCR, but may need that option enabled. The resulting document will have a readable text layer, although it is important to check for accuracy. JMU Libraries has scanners with OCR capabilities.
Important Note: OCR is not always perfect. Complex layouts—such as documents with images, shaded backgrounds, or tables—can reduce accuracy. While OCR enhances accessibility, the resulting text may still require manual review and correction.
Unable to scan with OCR?
If your scanner doesn't support OCR, you can still scan the document as an image and then use an OCR tool like SensusAccess to create a readable text layer.
Editing PDFs for Accessibility
Detailed guidance for editing existing PDFs for accessibility in Adobe Acrobat Pro is currently being developed. Because this process can be complex, you may want to consider whether an alternative format would better meet accessibility needs. Formats such as Microsoft Word, EPUB, and HTML are generally more flexible and accessible than PDFs.