OK, so Debian's passivetex and xmltex packages are sucking right now, I think.
Here's what I had to do to get the PDF output to work properly.

# rm -rf /usr/share/texmf/tex/xmltex/contrib/passivetex
# cd /usr/share/texmf/tex/latex
# wget http://www.tei-c.org.uk/Software/passivetex/passivetex.zip
# unzip passivetex.zip
# rm passivetex.zip
# cd /usr/share/texmf/tex/xmltex/base
# wget http://www.tei-c.org.uk/Software/passivetex/xmltex.tex
# mktexlsr
# cd /var/lib/texmf/web2c
# pdftex -ini "&pdflatex" pdfxmtex.ini
# cp 95NonPath /etc/texmf/texmf.d
# update-texmf

Sheesh. Don't ask how long that took to figure out.

-- Andy Wingo, 11 July 2002