I'm in a similar boat as Alexandro about it not being real practical for students to read entire PDFs during a quiz attempt. Providing them beforehand by adding them to the course homepage seems like it would be a better user experience.
HOWEVER, if you really want to include the PDFs in the quiz questions, like really super duper bad, like as bad as the girl from Despicable Me wants the unicorn stuffed animal, you can make it happen. Services like Scribd allow you to upload documents and then receive an embed code. See here for a similar explanation I gave to another user in the past. One more recommendation I would make is to put each question containing a PDF on its own its page within the quiz. Reason being is that the PDF is going to take up a decent amount of screen real estate. If you had multiple questions with PDFs on the same page, students could be scrolling for awhile just to finish the page of questions.
Happy 
oodling!
