If your PDF documents are "XFA-based forms", you can convert them into XDP files using "PDF Utility" service.
Otherwise, you have no other choice other than creating new templates from scratch.
How about opening the PDF in LiveCycle Designer and saving it as XDP? You can save the form as XDP. Not sure, whether it will have any impact at the running time. But you can give it a try.
yes you can open them in designer and select the "Interactive" option when importing it into designer
what is the use case for converting so many of these non xfa forms into xdp templates?
are these just data entry forms?