Same for me. I was able to annotate the first page. I'm running 6.10 beta 2 and OS X 10.12.1 Beta. Interestingly if I position pdf document between pages I can drag a shape over on to the next page and release the mouse. The box stays only on the original page, but I can then annotate the next page. I was able to do this with arrows, shapes, and the highlighter. Stamps between pages did not seem to allow me to annotate the next page below.