It is usually the manufacturer who numbers and labels the packages with barcodes. You can either make barcode originals yourself or hire someone to do it for you, such as a packaging designer, advertising agency, or a printing company.
If you want to print barcode labels yourself, you will need an “on demand” printer. We then recommend you to contact a supplier of label printers and software for creating barcodes.
If you get help from a printing company or a similar company please refer them to our size guide.