Matching of one order to one campaign explained
Currently, Penny Black only supports printing one insert per order.
While Penny Black does not offer native support for printing more than one insert per order, there is a workaround available: splitting orders after checkout.
Several apps are compatible with Shopify that do this, such as Order Split Pro. This app enables you to create rules for how orders should be divided after they have been placed. You can set specific criteria for any SKUs that allow for personalization, and if these items are included in an order with multiple products, the app will automatically split the order.
Please note that Penny Black does not provide support or guarantees for this method; however, our initial tests with this app have brought positive results.