Use this feature to save time setting up fields where your new PDF is substantially the same as one you already have. It's very useful where you have to use similar PDFs for your esign documents each time, but sender fields won't do it.
If you use substantially the same documents for esigning consider using sender fields - see this article on making PDFs re-usable on Legalesign with sender fields.
Upload your new PDF that will get the copied fields. Make sure you give it a different name to the PDF with your existing fields.
On the dashboard, click on the Docs icon and then Document Functions.