Example Use Case:
I would like to generate a QR image that can then be merged into a document with A5 Documents app. Then the customer will use the QR code and will need it be redeemed back into Salesforce.

-Background:
With A5 Documents, you can merge a URL of the image and then you just need a URL. Google has various google chart API’s that you can use to generate charts pretty easy with some data.  Here is an example of them generating a simple QR code which is just a URL: https://chart.googleapis.com/chart?chs=200×200&cht=qr&chl=https://ramseysolutions.com.

-How to Build Process:
You can create a formula field in Salesforce with Image() function to display a QR code for a record for example.  Or create a formula field that will create the URL for generating the QR code then merge that URL as the image in the document template.  And then you got a QR code merging on the document without any code or actual image needing to be saved.
A QR code basically is just a URL and when you scan it it accesses the url, so you just put a variable in the url such as http://a5-apps.com/qrscript.php?orderid=a0A0L00000JfKPN  and the web script gets the ordered and then can update Salesforce matching on that ID.