PDF my friend. I told my professors because I was docked for format errors, I would no longer be providing them a doc format because it was produced on office 2007 but they opened it on 2010. So MS's own fault.
Save as a pdf and lock that crap in. Same thing for business use. At least for use I've experienced before is that if it's going to a client, it's PDF. If it's within the office, whatever program your using since the whole company is going to have that.
This
PDF also fit on a 3.5" when a .doc wouldn't...