/usr/bin/ps4pdf is in texlive-latex-extra 2009-10ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../share/texmf-texlive/scripts/pst-pdf/ps4pdf
/usr/bin/../share/texmf-texlive/scripts/pst-pdf/ps4pdf