If you can deploy a user event script on picking tickets, you can make a small UE script that runs in the print context only to check that box. However, not sure you’d be easily able to then uncheck it afterwards, except maybe with a scheduled workflow or script to uncheck that box

Yeah, I could definitely see this as a possible workaround. In our case, we just send the PO's to our Shipping email address and CC a custom email address that auto prints any attachments that are sent to it. It's working for us.