Something seems to have gone wrong with generating the version 9.0 PDFs on the website: both A4
and US have no bookmarks tab. (I'm reading with Adobe Reader 7.0.0)
Just now I pulled from git.postgresql.org, and built the 9.0 and 9.1 A4 PDFs: these are both OK
(have the bookmarks tab).
(The 8.4.4 A4 PDF on the site is OK too)
ISTM this is worth fixing; without bookmark-tabs the PDFs are much less accessible.
Erik Rijkers