When an order is placed, you have one hour to cancel it before it is printed.
Once the one hour window has closed, it's no longer possible to cancel. At that stage the order is already en route to be mailed. The order status will be visible on the dashboard to the far right.
If an order is cancelled, the amount of the order is refunded into your thanks.io credit balance at the top right of the screen. (It will not be refunded to your credit card.)
If you cancel an order, there is no way to edit the cancelled order to re-send. You must create a new order from scratch.
There is no way to edit an order before it's printed once you place it. Any edits must be made before submitting it.