data security

5 departments r in the company.
Out of which, 3 departments (with 10 users each) r with secret data stored.
Data saved by a general user is sent to the executive of the respective dept.

Case should be, data once saved to the Executives’ PC, should not be accessed by the other users, including the creator.

How shoutld be the password management process for Executive & the general users.
The data is in Ms-office & in .pdf format.

Plz give reply.