I created a fillable Word 2013 document and protected it through Restrict Editing.



I selected 'Editing restrictions', and selected 'Filling in forms' from the drop down box.

I then selected 'Start enforcement', entered a password, and I was done.

Although it restricts editing text, it allows additional lines to be created by hitting the Enter key.

How do I protect ALL editing except for access to the fillable fields?

With the 'Filling in forms' protection applied, the only place a use can input anything will be in a formfield or content control. Of itself, that doesn't prevent the Enter key being used in one. To trap the Enter Key, see: https://support.microsoft.com/en-us/kb/211219

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]