Your screen shot suggests that Word is displaying the so-called Markup area, which will display if the document contains revisions and/or comments that are shown in balloons on the right-hand side of the document. If you rest the mouser pointer on the area on the far right, you should see a screen tip that displays "Markup area":
To permanently get rid of the area, accept all changes and remove all comments.
If you want to hide revisions/comments temporarily, you can do so via the Review tab.
