To save a lot of time and effort, try using the Compare and merge function
under Tools.
I tend to always work with copies of the files for safety and use the adage
"New for old", that is to say, open the "new" version and then compare to the
"old" into a new document.
Open the Review toolbar and skip through the document easily.
I use this everyday, find it much easier than visually trying to compare
documents side by side.
All the best, hope this helps.
DeanH