I would like to have a different unit system for my drawings than what I use when I am designing.   In my drawings I would like to have architectural units (ft-in fractions) in my drawings, but when I am designing I want to use straight inches with decimals.   It seems that I only know how to change the unit system for my entire work environment.  Is there a way to change the unit system for file types (drawing, part, assembly, etc.)?

Edit:  It is a shame I can only choose one correct answer because below is a lot of information that is useful.  I chose the most direct option as the "correct" answer, but please do read down below for a more complete answer base.