Prefilling form fields from internal client data before submitting for signatures

We have a process that is implemented through a wizard in a  web portal.  As the user progresses, they provide infotrmation that we will need to populate into a PDF and then submit for secure signatures.  Some of the information will be retrieved from our databases on login and preloaded for the user to either use or update.  The goal is to make the process as simple for our clients as possible.
While it is simple to put data into a pdf form template, I cannot figure out how to put that same data into an AdobeSign template or how to convert the filled in PDF form template into an AdobeSign document once it has bee filled in.

Is this doable?  I would think this cannot be that unusual of an ask.

Thanks in advance for your help.