Hello,
it appears that in org-mode 8.x the hooks org-publish-before-export-hook and org-publish-after-export-hook are no longer used. I did a search in the source code of org-mode 8.2.1 downloaded from
http://orgmode.org/org-8.2.1.zip, and then looked for one of the hooks with:
find ./ -name "*.el" -exec grep -H -n "org-publish-before" '{}' \; -print
No entries were found.
Instead, the method for customizing export seems to have been changed to accept a list of publishing functions in a project-alist:
find ./ -name "*.el" -exec grep -H -n "publishing-function" '{}' \; -print
gives the related code in lines 650-662 of file lisp/ox-publish-el.
If the above is correct, then the org-mode manual should be updated to reflect the change, at page:
Cheers,
Iannis Zannos