Unfortunately, there's no standardized way to add a QR code using the current version of our builder.  
The only place where you can add a JPG file (or other image formats) is the photo field in the personal information section. If your resume doesn't require a photograph, you can possibly upload a QR code there. 


What might work is using a PDF editing tool, which could potentially allow manual adjustments such as adding a new image or picture to your document.