Why Does the Appearance (or Layout) of My Document Change When I Open it on a Different Machine?
http://word.mvps.org/FAQs/Formatting/TextReflow.htm

Barnhill, Suzanne
Word MVP Site, The
2002

Abstract:

Because Word is a WYSIWYG application, it will always try to represent on screen the result you will get if you print on the printer that is selected as the default. Changing printer drivers will almost always change the layout at least slightly and sometimes radically. There are a number of ways to minimize the changes.