That is super strange!! The first thing I would try is deleting the file and reuploading it. Maybe even using a different internet browser. If that doesn't help then my recommendation is to contact Canvas Support and see if they can help. To do this click on the help link in Canvas and Report a Problem.
One of our faculty members is seeing this too. The downloaded PDF is fine - but every second page in the Canvas Doc Viewer is upside down.
It was uploaded multiple times in the course, and each time it appeared this way.
However, now the course has been changed around a little, and the PDF file is suddenly working properly. I'm not sure what the instructor did, or if Instructure pushed a hotfix. I can't reproduce it in any of my test courses any more either...