There are commercial programs available that will generate an "unencrypted" (i.e. with no password) duplicate clone of the encrypted PDF file in a matter of seconds.
On the Mac, I have used "PDFKey Pro" for years.
These are legitimate commercial programs, nothing illegal.
They do, of course, highlight the completely illusory sense of security you get from creating a supposedly secure PDF that "requires" a password.
You might get more information, and possibly other options, if you post to the Acrobat Reader Forum: http://forums.adobe.com/community/adobe_reader_forums
This forum is for discussing the Adobe Forums, themselves, so you are only hitting a tiny audience. While they have had ideas for you, the Acrobat Community will likely have many more.