This is a little hard to explain, I hope the attachments shed some light.
I have a word document (2010 but it doesn't matter the version) with many custom fields. When the document is locked and users fill out the field, the fill boxes add the slightest space under the fonts. When three or more custom lines are added, the space added will move lines at the bottom of the page down far enough that they move to the next page. See Attachment A.
When I take the protection off and fill in the form, the added space is NOT actually added and everything stays in alignment. See Attachment B.
Is there a way to stop this? I tried shrinking the fonts but that isn't working.