use an unsigned applet to view your files , make every file  requested a jar as a
resource to applet. Use Resource.get("your file ") as input for your doc viewer.
track user  downloaded files in another list (maybe in app scope). By this way
every time your doc viewer applet opens, its easy for your jsp page of your
applet, create and add jars as
resources ..... peh forget it. use an signed applet. the rest of all is your
imagination.