Section numbers and titles in PDF indexes

[Andrew McFarland <aamcfarland@gmail.com>]

I'd like to have a PDF index with section numbers and section titles
in the index instead of page numbers.

E.g instead of

widgets .......... 54

Have

widgets........3.4 Product Range

Is this possible? I can't see any easy way to do this. I looked at the
HTML index template, and only got confused.