Another important thing that can be done in this regard is text selection. Now it is again a myth as good PDF readers make sure that the highlighting is done no matter what. The other major reason is the fact that the PDF that is being highlighted has not been scanned properly.
It is for the same reason that the scanning never happens. Scanned PDFs are not regarded as real text by most of the PDF annotators online and offline. Some reasons for which the PDF scanning is required are mentioned as following: There are reasons for which such software programs are developed.
Why specialized software is required to highlight the scanned PDF.
