Once you have approved an order, there is still a chance to edit or cancel the order, but only before it is taken into production. You can cancel the order via "Orders" in Shopify or via the app.
In the app:
You can also change the shipping address before an order moves to In Production. To change the shipping address in the order details you need to go via the "Orders" option in Shopify, not via the SPOD app.
Once an order moves to "In production" there is no longer an option to edit the details of the order or cancel it. SPOD will not refund orders that need to have details changed, or be canceled.