we are looking for a product (hopefully a Progress product) to exchange information between any two systems and non Progress systems, sort like SAP iDOC. Any suggestions.
We also utilize rest and soap.
So you kind of answered your own question with Pro2 as it allows heterogeneous replication and IMO only reason to use it over OpenEdge Replication "Fathom" which is way better for ease of configuration and TCO. I hope you have a plan off HP-UX as it's a dead-end system right now. With Itanium end of life and HPE offering a container HP-UX (not sure why anyone use this) Linux seem the obvious direction. The company I'm working with are currently shifting from HP-UX to Linux.
Also you should get onto 11.7 for REST / SOAP; it's much easier to do this work now with the ABL.