Looking to upgrade from System 6 to System 7? Be sure to check out this support page that outlines how your documents will fair:
You can move documents between a Macintosh running System 6 and a Macintosh running System 7 without any problems. In most cases, your documents will not change their appearance. For example, if your document uses Times font in size 12, your document won’t change.
An exception occurs when you have TrueType fonts installed and you have documents using numerous odd type sizes.