I have just generated a class set of completion certifcates and each certifcate was generated in the same browser window as the class student list - this meant I had to use the browser back button to return to the list to generate the next certificate. Ok, I'm a real old guy and things may be different now, but back in the 1990's it was explained to me that best practice webpage functionality was achieved by always retaining navigation control on the page, not with the browser. And back then it was static HTML, not the dynamic pages we have now. So I believe that this process would be better if the PDF certifcates opened in a new browser window/tab.
thanks
Aubrey
PS and a check box batch certifcate generation process would be even better :-)