How do I restrict formatting changes to just the selected text?

[Gary]

When I apply formatting changes (left/right justify, font size changes,
etc.), they apply to the whole document. Clicking "undo" applies it to only
the teext that was selected. This extra step is obnoxious. Is there a
simple preference somewhere that I can't find that makes it do this?

 

[Suzanne S. Barnhill]

See http://word.mvps.org/FAQs/Formatting/WholeDocumentReformatted.htm