Which file do I modify to edit the user profiles page?
Tried Profile.template but nothing changes.
Well, it's in Profile.template.php, so if you didn't get a change, you were likely not editing the right file (e.g. editing one in a different theme to the one you were using)
or he forgot to clear the forum and browser caches...
Forum cache shouldn't affect that, it's a data cache; it's not like the old days where language strings were cached too.