The docs show
<footer>
{pageNum} / {numPages}
</footer>
The pdf/embed code looks for
div.page-footer
<div class="page-footer" style='height:30px'>
<span>Page {pageNum}/{numPages}</span>
</div>
This works.
The docs don't, and ... ugh... this has cost me a lot of time, trying to figure out if it was me, or phantomjs, or something else. Nope. Out of date docs.
Hopefully this can save someone else some time. Please patch when you can.