How to do sub contracting in Oracle Purchasing

please address how to setup following scenario

my client has procure to pay process only, no manufacturing

but he want some packing material printing do with third party supplier. basically paper provided by my client to the supplier, and third party supplier add the other printing material and print the packing item.

only printing charges payed when they receiving the label. 

i have few concern

how to add only printing charges

is this sub contracting process

papers are not supplier assets  how to maintain that.

thank you in advance

nalinda