Generate QR code

Generates a QR code for an invoice, by ID. The QR code is a PNG image in Base64-encoded format that corresponds to the invoice ID. You can generate a QR code for an invoice and add it to a paper or PDF invoice. When customers use their mobile devices to scan the QR code, they are redirected to the PayPal mobile payment flow where they can view the invoice and pay online with PayPal or a credit card. Before you get a QR code, you must create an invoice and send an invoice to move the invoice from a draft to payable state. Do not include an email address if you do not want the invoice emailed.