Documents (mathematical, scientific)

Academic papers and course documents are subject to the same accessibility requirements as websites if they're distributed digitally.  Many mathematical and scientific documents include notation and/or charts and graphs that aren't readily accessible to tools like screen readers (for a variety of reasons).

Graphics with text

When a graphic is distributed as an image (ie. formats like JPEG, PDF, PNG) any text that is part of the graphic becomes hidden from assistive technology and also may shrink to an unreadable size on smaller screens.