Below is an example of a working link back to a PDF which open from ADE into Web browser.
This is from a notes section.
Code:
<p class="notes">p.<a href="chapter11.xhtml#page_84">84</a> Of course, a dog’s sense of smell is well known . . . ‘The dog’s sense of smell’, <a href="http://www.aces.edu/pubs/docs/U/UNP-0066/UNP-0066.pdf"><span class="black">http://www.aces.edu/pubs/docs/U/UNP-0066/UNP-0066.pdf</span></a></p>