JEditorPane has to have an associated EditorKit to display specific types of content. You then register the specific EditorKit with a MIME type on the JEditorPane.
I don't know of any PDF, DOC, PPT, or XLS EditorKits... Instead of spending the time to implement an EditorKit to render the document inside a JEditorPane, most people just use Runtime.exec() to launch the file in it's associated program outside of the Java program. You could probably make EditorKits for all of these filetypes, but it would take a while.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.