Are you sure you're using "Acrobat" which is the "full" Adobe program which allows you to create PDF files.. It's an expensive program.. Or do you actually have Adobe Acrobat READER 5.0 which is free and only "reads" PDF files? Are you aware that 5.0 is quite old?
Many of the newer PDF files are created with updated PDF file advantages. If you're only using the "reader" part of the program, you can download and install Adobe Reader 9.3.4 from the link below..
Hope this helps.
Am running Windows XP on a DELL E310,using Adobe Acrobat 5.0. When I go onto IE7 and look for ANSC 7029H, which is a PDF fill-in-on-line form, and clicking on any of the responding web sites having that form, I get a "file is damaged and cannot be repaired" in an Adobe Acrobat window. Uninstalled and re-installed Acrobat 5.0 many times, no luck. Uninstalled IE 7 and tried IE 8, same results. Went back to IE7. Ran malicious program scan--computer clean. Clicking on other PDF addresses work fine. My son had no problem downloading the ANSC 7029H file and sent it to me in an e-mail. Trying to go to the hyperlink he sent me gets the same result. Any help will be greatly appreciated.