Under wp2print settings, there is a tab called "File modification." In this tab, what is displayed about an orders production status can be adjusted:
If admin checks the checkbox for a particular status, the wp2print will accept an amended artwork if the item in the order has that status. If the checkbox for a status is unchecked, then wp2print will not allow the customer to submit an amended artwork file.
If the item in the order is at a production status that allows submitting amended artwork files, then the customer will see the link "Add artwork file".