Use a cross reference to the text of the bookmark assigned to the formfield.
In the properties dialog for that formfield, check the Calculate on Exit box
to force the fields in the document to be updated so that the entered text
will appear in the cross reference.

You must protect the section of the document containing the formfields for
them to work.  The best way to control the amount of data that can be
entered into a formfield is to locate it inside the cell of a table with
fixed cell dimensions.