save as should do it. you can choose an older ver for compatibility.
then again it depends on what features or adding. in general and if generic it should not be a problem. if you added features from 2010 and not in the older that is different.
A lot of schools will have an agreement that you can get the software very cheap for free from school since you need it for classes.
its for school so its mostly, do you know anywhere i can get office 2007 professional in canada?