GNU/Linux Desktop Survival Guide
by Graham Williams
20190906 The diffpdf tool provides a graphical summary of differences between two pdf documents.
$ diffpdf doc01.pdf doc02.pdf
This will not find differences for image based PDF files that might come for example from a document scan. Such a pdf document contains an image of the text rather than the text itself, and hence it is not possible to compare text between such documents as is. See Section 66.8