When I saw this error, I thought it was a security setting on the pdf file.
so I opened it in my copy of Adobe Acrobat 6 Standard to view the security settings. There are none on the document.
I returned to the user's desk to look again and figured out that when I have Adobe Reader 6 set to open pdf files within the browser window, I can save a copy without error.
But when I have Adobe Reader set to open the pdf in the Reader application, not the browser, which is what the user prefers, I can't save a copy of the pdf. see error in question title.