What document types does Canvas convert using the document previewer?
You can preview several different file types in Canvas.
View Document Preview
You can view the number of pages in the document ; if there is more than one page, you can use the arrows to scroll to the next page. You can also zoom in and out  and view the document in full screen .
Here are the supported file types for the auto preview in Canvas:
View Process for Crocodoc and Document Previewer
If the submitted file is an assignment and Crocodoc supported file type, the file will be rendered by Crocodoc in SpeedGrader. If the submitted file is not an assignment or a Crocodoc supported file type, the file will be rendered by the Canvas document previewer or Google Previewer.