This question is about printing ALL content (including off screen content) of WKWebView. Currently (still, as of iOS 10.2 or OSX 10.12) there is NO working solution
I have exhausted every possible way to print the WKWebView directly with no success. The only workaround I can think of would be to convert the web page to a PDF object and then print said object. I will update with code if I get the workaround to work.