It would be helpful for troubleshooting if you can post some screenshots of the changed formatting and show or describe how if differs from the original formatting.
Also check whether a theme (on the Design ribbon) has been applied or removed; whether the Normal.dotm template (or the template on which the document is based, if not Normal.dotm) has been changed; and whether any style definitions appear to be modified. Each of these things can radically change the appearance of a document.