How to bring attachement in BPM

Hello,

We are on XI3.0 SP10.

This question concerns an RFC to SOAP scenario.

we are sending purchase order from EBP to XI by RFC (bapi).

Inside XI we use a BPM for mapping.

RFC doesn't support attachements.

How can we catch the attachement in the BPM in order to join it to the final message sent by the soap adapter?

Hoping for your answers,

Best regards,

Laurent.