How do I create a second label for an order on which I've already created a label?
In order to create a second label you'll need to delete the first label. To delete the label you've already created, hit the shipping labels button at the bottom of the order summary page, then hit the VOID text link on the right.
This will delete the label and the tracking numbers, and will restore the order status to unshipped. Then you will be able to create a second label. Remember that in settings/boolean options, your shipped label is turned on, so when you create the second label the customer will be notified that the package has shipped or will ship (depending upon the date you put on the label)