If you setup PDF based method to generate shipping labels, you can generate return labels directly from Teapplix.
Typically, to print a return label for an order, find the original order, click on "RMA" to create a copy of the order, set the RMA Code to "Return". The order will be automatcially be put in the "Return" Queue.
Then, click on "Return" under Open Orders to go to Return Queue and click on the corresponding button to print the return label. The buttons to do so are called "USPS Return", "UPS Return", or "FedEx Return". These buttons are also displayed when you view the "Hold" queue or USPS Domestic | USPS Intl | UPS | FedEx built in queues.
Once the return label is generated, you can save it to a PDF file and email the label to your customer afterwards.
Please note, you can not generate a Return label for international orders. These can only work for US Domestic.