Automatic language switching works because the document is coded for it. I'm guessing that QRead is just getting the text out of the PDF file and it's not responding to those codes, either because it just doesn't or because they're no longer there. So you'd have to contact the developer about adding that feature.

So for example, even if I have automatic language switching turned on and I write "es drickst de ganze Daag", it won't read that with a German voice, because it's not coded as German, as it might be on a website. Well OK, it's Deitsch (Pennsylvania Dutch/German), so it might not recognize it even if it was coded, but still.