How to create DFF in process requisition page?

Summary:

We have a requirement to create DFF's in the process requisition page.

When the buyer is processing the Purchase requisition to Purchase Order from the process Requisition page, he need to capture his name in as a DFF value. We need this because when the buyer is reassigning the PR to another buyer there is no provision to capture the buyer to whom it was initially assigned.

How to create additional fields to capture the initial buyer in the Process Requisition page?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):