I bought a pdf book last year and had no problem reading it for a few months then all of a sudden I could no longer open it and to this day. Any other pdf download off internet I can still open and read, except for that particular book. Operating system i

I bought a pdf book last year and had no problem reading it for a few months then all of a sudden I could no longer open it and to this day. Any other pdf download off internet I can still open and read, except for that particular book. Operating system is Windows 7 Home Premium, Adobe Reader XI 11.0.07.  When trying to open file I get msg "You did'nt login or your session has expired. Please log in to read this document for the first time". (Like I said I have read it before). So I log in but that prompts me to give the name of the file I want to export or convert to Word or something else, which is not what I want to do of course. I have not purchased any service from Adobe or Acrobat as I only need to read. Thanks for your help..