That was taken from PGP 7.0* manual!!!

Additional Decryption Key properties:

To access the ADK panel for a particular key, select the desired key and then choose Properties from the Keys menu. The Key Properties dialog box appears, as shown in Figure 4-2 on page 6*. Click the ADK tab. The ADK panel appears. (Note, if there are no Additional Decryption Keys associated with the selected key, then the ADK tab does not appear.) The ADK panel lists all Additional Decryption Keys (ADKs) for the selected key.

__ADKs are keys that allow the security officers of an organization to decrypt messages that have been sent to or from people within your organization. There are two types of keys: incoming additional decryption keys and outgoing additional decryption keys.____

___NOTE: Although the security officer should not ordinarily use the Additional Decryption keys, there may be circumstances when it is necessary to recover someone’s email. For example, if someone is injured and out of work for some time or if email records are subpoenaed by a law enforcement agency and the corporation must decrypt MAIL AS EVIDENCE FOR A COURT CASE._