Saving form fields

I was wondering if there is any way to save the form fields in a document. I don't mean the data in them, but rather the field layout itself.

The reason I'm asking is that I have a document that undergoes slight changes in the layout every so often, and everytime I edit the original file (in InDesign or Illustrator) - adding, editing, or removing elements, text, etc. the file gets stripped of the form field information, meaning I have to start from scratch everytime, adding the form fields again.

I've tried to copy the fields from the old PDF (⌘+C) and pasting in the new PDF, but it doesn't work properly - it only pastes a couple of fields on a seemingly random position in the new document.

Any help would be appreciated!

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