How do I decrypt a password-protected PDF on OSX?

There's a command-line tool called qpdf that can remove the password encryption from your PDF files, even in cases where Preview won't let you save a copy of or export the PDF.

Installing with Homebrew

1. Install Homebrew if you haven't already.

2. Install qpdf on your system by typing the following in Terminal:

   brew install qpdf
   

Installing with MacPorts

1. Install MacPorts if you haven't already.

2. Install qpdf on your system by typing the following in Terminal:

   sudo port install qpdf
   

Usage

Once qpdf is installed, use it to decrypt the file by typing the following in Terminal:

qpdf --decrypt --password=xxxxx encrypted-filename.pdf decrypted-filename.pdf

You can then open decrypted-filename.pdf in Preview to verify that it worked!

Nathaniel's answer inspired me decide to try File/Save As... in Preview, which let me save a copy of the PDF with no password.

I'm surprised that it was that straightforward, but it worked.

For those looking for a loop hole to save password protected PDF's in OS X 10.8.3 ... I found Opening the PDF in Chrome then Printing it to PDF using the Chrome dialog did the trick.