Handle "Bizarre Swelling of the Right Margin Syndrome"
The Problem:
Okay, tell me what's going on. I printed the first few pages of the new sales report we've been working on, and the right margin is about two inches fatter than it should be. The bottom margin is bigger too. Did I hit a secret keystroke for the Insert 
Pork At East and South command while my espresso was kicking in?
The Solution:
It sounds as though the document contains tracked changes (or comments), the view is showing "Final with markup" or "Original with markup" rather than "Final," and the pages you printed don't have any tracked changes or markup on them. Word is reserving space in the right and bottom margins for the change balloons and notes, even though there aren't any on these pages.
To fix this problem, either get rid of the tracked changes (accept them or reject them, as appropriate) or switch the view to "Final" in the "Display for review" drop-down list on the Reviewing toolbar.