You can create packing slips from the Orders section.
Please follow the simple steps below in order to create packing slips.
Step 1: Open Simple Invoice from your Shopify store’s “Apps” section.
Step 2: Select the order you wish to create a packing slip, select print, download, or upload (Premium Plan only), and select the Packing Slip option from the dropdown menu.
Important Note: You can only print, download, or upload (Premium Plan only) documents. It is not possible to directly send Packing Slip. You can manually download and send it to your customer.