You could use "Protect for forms" to lock sections of the document, but that
does take away a lot of Word functionality (including the spell checker) so
it's not really a good way to control a template.

Best approach is usually to customize Word to make it as easy as possible to
do the "right" thing, and more difficult to do something wrong. For
instance, you could remove Insert > Break ... from the menus, and maybe add
the command for Page Break Before, or a macro to insert a section to your
design.

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Margaret Aldis - Microsoft Word MVP