It seems like continuous multipage display is your main problem here with the royalty free libraries.
Just an idea : One option may be to use QuickPDF to convert the PDF into a multipage PDF file and then write some code yourself to simulate a continuous multipage scolling. If you need zooming and other PDF display features then this may not suit your needs though. Another option is to use a thumbnail window down the side to help users navigate and show single page in the main window. You may not have too many other options as you seem to have used all of the PDF libraries that I am aware and a couple more.
It all depends on what your viewing and printing requirements are of course.