Make sure that under the Page Setup Options, Header/Footer tab, the Scale with Document is not selected.
Also, certain page settings can be set/changed based on the default printer Office sees.
If you and your coworker are using different printer drivers/printers, you can experiencing some weird differences.

Thanks! We've started working on a different background that is not one full-page image, but a logo at the top and typed-in footer address, web site, etc. at the bottom. For whatever reason this one seems not to have the scaling problem.

I'll have to experiment with the "Scale with Document" off and on, and we use the same printer/copier situated between us, but since her computer was newer, it's possible we have different drivers. Good tips.

Thanks,

Ann