Hi, there... I did register two of my books: "PDF Explained" and "Developing with PDF". Selecting the first one in my books list did offer my an upgrade button. BUT: There is no discount given in the shopping cart.
The second book does not even offer such 'upgrade discount' button. - BUT it should!!!
Again, and again such problems occur at your page --- PLEASE try to fix this up ...
I apologize that you are facing difficulty with getting the upgrade discount when registering your print books. I will e-mail directly and will provide you with a discount code that will enable you to purchase these ebook for $4.99.
Customer Service Representative