I've heard reports of users opening PDFs in Moodle and only seeing the first page. I believe this is related to how your browser (likely Chrome) is handling PDF files. First, make sure you have the Adobe Acrobat Reader extension installed in Chrome. Here is more information on making sure the PDFs are opening in your browser using the Adobe Reader.
If all that is more than you wish to deal with, you can also try switching your browser to Firefox!
Josh Moon
Educational Technology Specialist
Educational Technology Specialist