We are just starting to experiment with this now. Our students will have iPads, which will have Notability. I realize that Notability is not available for Chromebooks, but with a quick search it looks like there are some apps that will let you annotate pdfs. For us, it looks like students will download the pdf, write on it, and then upload it back to Canvas for things we want to grade.
Doing some testing with another teacher it looks like this will work for us, though it may take some training for the students because it's a little clunky in the Notability->Canvas direction.
I think there's also an idea open for voting right now about annotating directly on pdfs from within Canvas, so you might want to search for that and vote it up. Here it is: .
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