While I still hope for a quick fix for the standard pdf reader, I can report that evince from extras-devel is a good alternative (have been using evince from Easy Debian so far, but the native version is more convenient). Does anybody know how to make microB use evince in place of the standard pdf reader when opening pdf documents in the browser?
application/pdf=hildon-evince.desktop
sudo update-mime-database /usr/share/mime