This documentation is for the older version of the WooCommerce PDF Invoices, Packing Slips, Delivery Notes, and Shipping Labels plugin. If you are using the new version of the plugin, please note that this documentation no longer applies to you. Find the relevant documentation from here :

WooCommerce PDF Invoices, packing slips and credit notes plugin | WooCommerce Shipping labels, Dispatch labels and Delivery notes plugin | WooCommerce Address labels plugin | WooCommerce Picklists plugin | WooCommerce Proforma invoices plugin | Customizer for WooCommerce PDF Invoices