Canvas now allows students to add annotations to PDFs used in an assignment right from within the Canvas mobile app.
This feature allows students to create annotations in files, such as in-class worksheets, before submitting an assignment. Students can open the file either from a link in Assignment Details or within course files, leave annotations, and submit the annotated file.
Possible annotations include highlight, underline, strikeout, squiggly, drawing, free text, and image.
For more details on how to do this, see Student Annotations in the Instructure Sept. 28 mobile release notes.