if you have set your form up with FORM FIELDS that you define, you LOCK the document. I used to create templates like this when I was working. When you opened a new document based on that template, the starting position would default to the first form field, and you type your text or numbers, etc.
Defining the field - you can set for normal text and limit the number of characters (I believe it's the 2nd window down directly under "normal text" - right hand windows (2nd down) you can specify the format of the input. You can even create HELP text as reminder (customize your own and type text in the box) and give that field a label you can recognize. It's pretty neat to use.
Cynthia