Don't let users change accepted orders!
It's annoying if you check an Order for it's printability.
Make all adjustments to the project, accept the Order and when the customer pays the Order you see, that he added some new files you haven't ever seen.
You shouldn't totaly disable the function to the user, but as soon as the Hub has accepted the order, the user must ask for permission to change files again.
Or you let the user make changes, but it doesn't get updated until the Hub validates it.