Mac
http://www.evenbalance.com/index.php?page=pbsetup.phpIn pbsetup.run, choose File > Add Game, then choose Call of Duty 4 in the popup button. You will want to choose the Call of Duty 4 Data folder as the target like in the image below:
After you've chosen that, choose File > Check For Updates and it should download and create a pb folder inside the Call of Duty 4 Data folder.
Or is the version you got from the Mac App Store a single application bundle? You may also need to change the permissions on it so that it can successfully write the pb folder.
or
download the pb update program and point it to this for your call of duty program location:
/Applications/Call of Duty 4.app/Contents
Next locate your Call Of Duty 4 program in applications, right click and select Show Package Content.
Next right click on contents and click get info.
Drop down sharing and permissions
Now click on the little padlock bottom right of info, admin login now
Change permissions to read and write and make sure you do this to all subfolders by selecting the little wheel thing.
Then run update in the pb update program and bam you've done.