How to disable a Preview PDF encryption?

I password protected several preview PDF's of mine and I can open them since I set the password; but I want to remove the encryption so they are no longer password protected. . . and I can't. I also can not find any information on this in the Preview Help.

Am I forever going to have to enter my password each time I want to open these files now?

I am the administrator of this machine. I encrypted the files and don't want to rescan them all to regain non-password file access. Help!

iMac Mac OS X (10.4.7) Intel Based Core Duo