If you only want it for editing purposes, with no effect on the actual ePub (i.e., no possibility of linking to a page), you could just use XHTML comments, and you can be as verbose as you want:
Code:
<p>Once upon a time there was a little girl
<!-- page break here, page 5 ends, page 6 starts,
with page number in the bottom right and a coffee
stain near the spine -->
who lived in the forest.</p>