Thanks so much for posting on the forums! I looked into this and there isn't a way to add barcode lines to orders made using the order printer app, though I am going to make it a feature request as its a great idea!
You can use the Shopify barcode printer app and Dymo LabelWriter 450 to print barcode stickers that you could stick to your packing slips!
Alternatively, there are some other barcode apps that you can check out here in the app store!
I use that same method in my app Order Printer Templates, which of course you are welcome to use if you want to save time/headaches.
Let me know if any questions come up.
I'm trying to add a barcode to my invoice but rather than a barcode for the product, I'm hoping to add a barcode for the order number so i can utilise a "Scan to Print" feature with my courier. How would I go about adjusting the info from Bjorn to do this?
Any help would be much appreciated,