I have 141 pages in a book that is on its way to me right now
When you are on step 4, edit your book... once you are in the pages you will see a plus and minus sign on the bottom right that is how you add or remove pages... make sure you do it before you get to the end and start doing it though
if you forget just click the question mark on the top right, all the info is in there
HTH
and fwiw, I love all my photobooks from them