This article describes how to import a public and private keypair into PGP Desktop for Windows.
153196 - Backup/Export PGP Keypairs
180127 - HOW TO: Add Existing Keyrings to PGP Desktop for Windows
180129 - HOW TO: Access the Backup Keyrings Created Automatically by PGP Desktop for Windows
153195 - "It is not possible to decrypt this message..." Unable to decrypt - Keyring does not contain usable private keys
180130 - HOW TO: Reconstruct Your Private Key for Windows
153511 - Additional Decryption Key (ADK) Guidelines for Symantec Encryption Management Server
153477 - Import an ADK to Symantec Encryption Management Server (aka PGP Universal Server)