Password protect documents for leavers

The ability to password protect documents is available for active employees. However, it is not possible to password protect documents for leavers. I do not understand why it was not enabled for leavers as it is common to have to forward P45s as employees find it difficult to log into the portal (due to the need to activate 2 logins for Access as well as Paycircle). I am having to use an external tool to password protect documents for leavers.