Hey there,
I am facing difficulties when trying to get the Purchase Order output with an edited/copied web-service.
I have designed a PO document layout with the Adobe Livecycle Manager. At first, the layout used the standard web-service FDP_EF_PURCHASE_ORDER_SRV. Printout with this service worked without problems, and the layout managed to display most of the required document data (I displayed the PO document with the created layout in transaction me22n - Messages - Display PDF Document).
As the default web-service lacked some fields, that I needed (for example Price Per Unit), I made a copy of the service (in transaction SEGW) and added the required field and tested the service successfully in gateway client (The Price Per Unit field was there).
After doing that, I swapped the default service with the enhanced copied service in the layout's properties:
But after swapping the service, I get an error "Key parameter PurchaseOrder has not been provided." when trying to display the PO document in me22n.
Have I missed something in the configuration (e.g. - do I need to set the new created service as the PO print service somewhere) ? As the custom web-service is a copy from the default service, with just only one field added, there should not be much that has changed.
I hope there's somebody who would help me with this problem. 
Thank you,
Mario.