On the Reviewing toolbar, you can click Insert Comment. If you're in
Print View, this gives you a balloon in the margin where you can type
stuff, which doesn't become part of your main text, and is identified
by your username and the time of insertion. You can show or hide
comments, and you can delete them individually or all at once.
Could be useful for a novelist who needs to remember whether plot
incident X was foreshadowed at point A!
(If you're in Normal View, they go in a panel at the bottom. Much less
helpful.)
If you print your document with comments showing, the printed page
shrinks so that the balloons will fit onto the paper.
