When PDF documents appear blank, you should check your settings and always keep your device, browsers, etc. updated.
-Try accessing with another device
-Check your antivirus. Many times the antivirus you have installed can interfere with you viewing the files correctly. Try disabling it to check.
-Try accessing with another browser
-Update your version adobe reader
-Verify that you have the option to view PDFs in the browser. Access your browser settings and look for how you have your PDFs displayed:
Click:
Make sure it is disabled:
*If the course organizer has made the document downloadable, check if you have it in your folder where the downloads arrive.