highlight and add in-line notes to scanned articles.
Sometimes I only have access to a scanned PDF -- for example, one that was retrieved through interlibrary loan. For such PDFs, it would be nice to be able to add in-line notes and highlighting even if ReadCube is unable to recognize the text.
Christian REGIS commented
This is the only thing missing really Readcube to match Mendeley or Papers. It would be wonderful. I have a lot of pdf files scanned.