Prawn/QRCode
A Ruby extension for the Prawn PDF-generation library that adds simple QR-code generation and rendering to a Prawn document.
Prawn/QRCode is a small extension to the Prawn PDF library that simplifies adding QR codes to a generated PDF document. It requires Prawn version 1.0.0 or later and installs as a Ruby gem.
The gem's own examples folder contains a full set of usage examples for rendering codes into a document. It is released under the Apache-2.0 license, and notes that QR Code is a registered trademark of Denso Wave, which it credits as the format's owner.