Last Updated On September 06, 2019
Text selection gestures may not work with image-based PDFs, such as scanned PDFs, and PDFs converted from images.
These image-based PDFs do not show any textual information except for image information. Therefore, text selection gestures such as underlines, circles, and parentheses may not work.
However, image capture gestures such as square, L, and etc. can be used with image-based PDFs.