The most likely explanation is that your fonts and printer drivers are
different than the Windows versions (that happens among WinXL users,
too). Make sure your standard font (Preferences/General) is the one
they're using, or at least one common to both platforms, such as MS's
Times New Roman. If they're using a font that's not available on your
system, XL will attempt to substitute a "close" one, with mixed results.
Some differences will probably not be able to be reconciled - XL isn't a
page layout application on either platform.