Accessibility for External PDFs
The term external PDFs means a pre-existing PDF file for which you do not have access to the original source file. The source file may have been written in Word, Google Docs, or LaTeX, and perhaps you no longer have access to that file. Making such PDF files accessible is challenging but not impossible. Some tips are below, see also the External PDF files page written by Yao-Yuan Mao.
UDoIt in Canvas
The university had purchased UDoIt, a plug-in for Canvas that scans Canvas course content and files, identifies accessibility issues, and provides guidance to fix problems. It can be used specifically for identifying and fixing problems in PDF files. The following steps are suggested by Yao-Yuan Mao's instructions for creating accessible PDFs with UDoIt.
- Upload the existing PDF file to a Canvas course. For content that is not associated with a course you are teaching, you can create a Canvas test course as a place to upload and convert files.
- In the course navigation menu follow the link to UDoIt. It will start scanning the content, which can take some time.
- Choose the Review Course Files tab. Find the PDF file you just uploaded and click the Review button.
- You can convert the PDF file into an accessible Canvas page, an accessible HTML page, or have it auto-tag the PDF to make it accessible while retaining the PDF format. You can review the generated document and replace the original file with the new accessible version. You can find the generated versions in a folder called Alternate Files in the Files section of the Canvas course.
- For more information on how to use UDoIt, see the ULEARN Accessibility Guide put out by its creator. The accessibility guide highlights each issue that UDoIt can detect and provides guidance on how to fix them.
Adobe Acrobat Pro
Adobe Acrobat Pro can be used to check accessibility features in an existing PDF file, and often to add those features if they are missing. You can request access to Adobe Acrobat Pro through the university.
- Open the PDF file in Adobe Acrobat Pro.
- Got to Tools > Accessibility (sometimes called Prepare for accessibility)
- Select Check for accessibility to see ift he PDF has accessibility features.
- Use the Accessibility Checker to identify and fix any issues.
- If the PDF file is missing tags, you can use Automatically tag PDF.
- If there is missing alt text on images, you can add them with the Add alternative text option.
- You can also add or edit the document title metadata.
Note: Re-tagging a PDF that was already tagged well (for example, by a LaTeX tagging setup) will sometimes make the tagging worse. If possible, fix issues at the source document instead of re-tagging.
Mathpix & Mathwrite
For PDF files with many math equations, AI tools are relatively good at converting them from PDF back to LaTeX. If the conversion succeeds you can then use the tips in Generating LaTeX Accessible PDFs to re-build the PDF in an accessible format.
AI tools that we have found particularly useful are Mathpix and Mathwrite.
As of this writing, Mathpix has an API that is very useful for programmatically converting large numbers of PDFs into another format. It can also convert PDF files into accessible Word documents, and its own format of Markdown called Mathpix Markdown.
Both services also claim to be able to convert handwritten notes into LaTeX and other formats.