The text in form fields in a protected document cannot be formatted; if you
want users to be able to format text, insert a section and leave that section
unprotected.
From Word 2003 Help:
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On the Tools menu, click Protect Document.
In the Protect Document task pane, under Editing restrictions, select the
Allow only this type of editing in the document check box, and then click
Filling in forms in the list of editing restrictions.
To protect only parts of a form from accidental changes, click Select
sections, and then clear the check boxes for the sections you don't want to
protect.
Note To protect only parts of a form from accidental changes, those parts
must be in separate sections. (On the Insert menu, click Break to create
section breaks.)
Click Yes, Start Enforcing Protection.
To assign a password to the form so that others don't accidentally change
the form's display content, type a password in the Enter new password
(optional) box, and then confirm the password. Users who don't know the
password can still enter information in the form fields.
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