From the User's Guide:
Uninstalling PGP Desktop
To uninstall PGP Desktop
1 In PGP Desktop, from the PGP menu, select Uninstall. A confirmation dialog box is displayed.
2 Click Yes to continue with the uninstall process.
3 You are prompted to authenticate as the administrative user of the Mac OS X system from which you are uninstalling PGP Desktop. Enter the appropriate password, then click OK. The PGP Desktop software is removed from your system.