Mac OS X and Symantec Encryption Desktop :

Mac OS 10.4 - Tiger
9.8.0
9.8.1
9.8.2
9.8.3
9.9.0
9.9.1
9.12

Mac OS 10.5 - Leopard
9.8.0
9.8.1
9.8.1
9.8.3
9.9.0
9.9.1
9.12
10.0.0
10.0.1
10.0.2
10.0.3
10.1.0
10.1.2
10.2.0
10.2 MP1
10.2 MP2
10.2 MP3
10.2 MP4
10.2 MP5 (recommended)
*10.2.1 (not supported)

*Mac OSX 10.6.8 and above is recommended for Symantec Encryption Desktop 10.2.1.  The Symantec Encryption Desktop 10.2.1 Release Notes incorrectly state Symantec Encryption Desktop 10.2.1 is supported on Mac OSX 10.5.  Symantec Encryption Desktop 10.2.0 MP5 is recommended for Mac OSX 10.5.

Mac OS 10.6 - Snow Leopard
10.0.0
10.0.1
10.0.1
10.0.2
10.0.3
10.1.0
10.1.2
10.2.0
10.2 MP1
10.2 MP2
10.2 MP3
10.2 MP4
10.2 MP5
10.2.1
10.2.1 MP2
10.2.1 MP3 (recommended)
10.2.1 MP4 (not recommended)
10.2.1 MP5 (not recommended)
10.3.0 (not supported) *

* NOTE: Symantec Encryption Desktop 10.3.0 (formerly PGP Desktop) is not supported on OSX 10.6.

Mac OS 10.7 - Lion
10.2.0 (not recommended for Lion)
10.2 MP1
10.2 MP2
10.2 MP3
10.2 MP4
10.2 MP5
10.2.1 MP2
10.2.1 MP3 (Recommended for 10.7.4 and below)
10.2.1 MP4
10.2.1 MP5
10.3.0 (Recommended if running Mac OSX 10.7.5)

Mac OS 10.8 - Mountain Lion

Mac OSX 10.8.0 through 10.8.2 -Symantec Encryption Desktop 10.2.1 MP5*
Mac OSX 10.8.2 - Symantec Encryption Desktop 10.3.0 (Recommended for both Mac OS X 10.8.2 and 10.8.3) .
Mac OSX 10.8.3 - Supported with Symantec Encryption Desktop 10.2.1 MP5 (build 5033) and 10.3.0 (8741) and above.

*In order to install a Customized, or Managed Encryption Desktop 10.2.1 MP4 installer for PGP Universal Server communication on Mac OSX 10.8, special steps must be followed.  Please see the following KB for information on creating this installer:

HOWTO79578

NOTE: Standalone clients for Encryption Desktop 10.2.1 MP4 that do not communicate with a PGP Universal Server do not need to follow these same steps.

Mac OS - PowerPC

Please note that the "PowerPC" platform is only supported until PGP Desktop 9.12. Support was removed since 10.0 which only runs on the Intel platform.

This is documented in the release notes for 9.12 and 10.0:
9.12 supports Apple Mac OS X 10.4.x, 10.5.x (Intel or PowerPC)
10.0 supports Apple Mac OS X 10.5.x or 10.6.x (Intel)