Well, you use the showDocument() methods in AppletContext (you say getAppletContext().showDocument(URL, "frame") to show the URL in a frame named "frame".) As far as clicking at X, Y, that's just a matter of handling the mouse events.
Not sure what you're thinking, but in any case, showDocument() tells the browser to open a document, just what you want. You can have the document show up in a particular frame, as I said, or it can just replace the page the applet is on if you use the one-argument version.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com