Hi we recently applied PR application for my in-laws (Family sponsorship - PGP). In our case, we only scanned the pages with bio, contact info, visa/stamps, notices, amendments, basically any pages that has information other than page number and standard watermarks and avoid scanning the blank pages that have nothing (other than page number and standard watermarking). This is mainly to reduce the file sizes. For one passport, we had to reduce the size with the adobe software and the size was just enough to be unloadable. Note that system wont accept any files that are more than 4 MB.
Just to be on a safe side we explain in a cover letter why we did not scan the blank pages.