Line numbers in Microsoft Word

Today I learned that you can display line numbers in Microsoft Word. Just go to File->Page Setup, click on Line Numbers, check Add line numbering and adjust the rest of the options as needed. I wonder how many people know of this feature?

Here's some more info on it: Office Space: Adding Line Numbers to a Microsoft Word Document.

In case you were wondering, OpenOffice.org Writer can do line numbers too (at least, version 2 that I have installed can). It's a little easier to find: Tools->Line Numbering...