Shipping Label Workflow
Shipping labels can be produced at the time a shipment is created, or later. Shipping labels are stored in PDF format and downloaded to your computer. Depending on your browser settings, you can open the file at once and print the labels. Each shipping label appears on a separate page in the PDF file.
When you create a shipping label, Magento prompts you for information about packaging you want to use (type, size, etc.) and which products go with which package. When you finish, Magento connects to the shipping carrier web-services, creates an order in its system, and receives the shipping and tracking number(s) for the shipment.
After the shipping label is generated, the new shipment is saved and the label can be printed. If the shipping label cannot be created due to problems with connection or any other reason, the shipment is not created.
The logic for tracking numbers differs when shipping labels are created for merchandise returns from RMA managing pages. In this case, old tracking numbers are replaced with new ones.