Hello Sarah
As my understanding, once you have created a Purchase Order, this is not printed automatically. If you go through the Shopping Cart and you create a PO, once you order and save it you have the option to print a preview manually at the top left corner of your display, but there is not automatic printing, not unless you program a default setting to do it from the back-end system in my opinion.
I am new with the SRM SC so in case I am wrong someone will correct me eventually 
I hope this helped
Have a nice day 