Double a small length of thread and tie it to a jump ring. Make sure the opening in the ring isn't covered by the thread. Glue the thread to the paper stack with the ring sticking out, then keep adding layers on top until the pendant is the desired thickness.
To seal it, you can brush it with polycrylic or Triple Thick. To make a shiny, glass-like surface, try some Mod Podge Dimensional Magic, Aleene's Paper Glaze, or Diamond Glaze. Test the products first on a scrap of paper to make sure colors won't bleed.