Word 03 on XP SP2 Box

For reasons I cannot explain, I noticed I had forgotten to insert page
number at the beginning of my document, and remembered I need to do it
before printing and making my footer. I can't because it's the only item on
the Insert menu ghosted out. How can I unghost it? Do I have to close the
document and then open it? Equally important, how did it get this way so I
can avoid this in the future.

Thanks very much,

Chad Harris