I have an important problem right now. I downloaded a book using Google Play and it downloads in .acsm so I use Adobe Digital Editions because the program create a "copy" in its folder in .pdf format to use it. The problem is everytime I try to open the pdf, an error message appears, "The selected document can not be open". I can't use programs like "Calibre" to try to change the format or something. I don't know what to do.
I encountered the same problem, only in my case the error occurs when I try to open a document in Epub's format.