You can print or download documents like Credit Notes, Packing Slips, Return Forms from the “Orders” page of Simple Invoice. Just click on the “Apps” section of your Shopify dashboard and click on “Simple Invoice” from the list. You’ll be redirected to the “Orders” section of Simple Invoice. Click on the order you would like to process and change the document type from the left menu.
Additional info: You can only print or download documents. It is not possible to directly send Credit Notes, Packing Slips, or Return Forms. You can manually download and send it to your customer.