QR code URL format
QR codes can encode a URL so that when scanned it will direct users to a specific website. In this case, you will want it to go to your website with the gift card code as part of the query string.
By default, the Redeem URL is your shop page that is defined under WooCommerce -> Settings -> Products -> Shop Page.
As long as you include the pw_gift_card_number query argument it will automatically apply the gift card to the cart.
https://www.yoursite.com/?pw_gift_card_number=VGZR-TEBW-BT9Z-XCUQ https://www.yoursite.com/shop/?pw_gift_card_number=VGZR-TEBW-BT9Z-XCUQ https://www.yoursite.com/product/example/?pw_gift_card_number=VGZR-TEBW-BT9Z-XCUQ
When you send the list of gift cards to the printer, explain that the QR code needs to point to the URL for your site along with the gift card code.