How to highlight the text changes to the supervisor?
In Word, you can use the 'track changes' function. 

It depends a bit on the amount of changes you're making though. Track changes will mark every cut and paste, every comma and deletion of every double space. This can make it too difficult to read. Personally, I've resorted to just underlining the most important changes so that my supervisor can see them easily, and adding the occasional comment bubble.