Button for document download

There currently isn't a direct way to have a button trigger a document download event.  Some people have had some success using the "use card as button" design pattern, wherein you use a CardLayout (which actually has an underlying link), though if you're trying to nest it right next to another button, I'm not sure how well this would work either. 

One alternative possibility to consider (though this is a slight change to your design), is that the button could trigger the opening of a Document Viewer Field which shows the PDF - then the user could do what they want with it from there.  But that's about the only thing I can think of off the top of my head.

I'm not really clear what you mean when you say "I want to print the QR code by selecting the printer".  Do you mean like having a dropdown with printer options, and choosing one of them triggers a document download?  If so, then there's also no way to do this directly, and I'd defer to my alternate suggestion above.