I remember, that it was just a resignation to prevent an impeachment. So I guess that his pardon was just a precaution or something. But almost everyone is sure that the pardon was the payment for Ford’s presidency.
Here is the definitive answer. I was wrong. It is for a conviction vs offense. My error. My bad. They also have a section on military pardons.
http://www.justice.gov/pardon/pardon-information-and-instructions