Hi Evan,
I recon he means that the headers can become an index for the document, that is a page tree in pdf to navigate to the various headers at the beginning of the document ...
you could give the a select option upon pdf export which headers should be included in the index
(e.g. H1 = chapter H2 = section, H3 = subsection etc.)
This is common practice for online publishing (leanpub.com)