A QTextDocument supports internal linking, for example by inserting the following html:

<a name="top">Top of Document</a>
other html...
<a href="#top">link to top</a>

But when exporting QTextDocument to PDF, internal linking doesn't work in the resultant PDF (external links work properly when exporting to PDF). 

It would also be nice if Qt supported span id's for exporting to PDFs (it appears to with QTextDocument). Ie.

<span id="top"></span>

Giuseppe D'Angelo of KDAB confirmed that this is a bug and that the code doesn't handle it.