Display pdf files

I have another issue, and I hope to find an answer on this forum. Canvas is not reading the pdf files when I upload them to course files, so the files won't embed in the assignments. I tried to do this in a regular assignment, and before this, I used https://pdfliner.com/form-4473-firearms-transaction-record to modify my pdf files and add some details. I don't know if I explained it right because I'm kind of new at this, but I can't make this work no matter how I tried. How do I embed a pdf file into an assignment?