The DocViewer currently gets hopelessly bogged down by larger PDFs, especially when they contained recognized text.
For example, a 150 page 8 1/2 x 11 document scanned at 300 dpi with recognized text takes more than ten seconds to load and results in frustratingly choppy scrolling. Anything longer than this just is not readable within Canvas.
This has teachers turning to Google Drive or similar apps to host their documents instead, since all of these can render much bigger PDFs than this in the blink of an eye!
It's easier on students if they can just view documents within Canvas without having to download them or open them from somewhere else. It'd be great if Canvas could handle displaying these larger PDFs.