SETUP - P4/32bit with Debian net-install, Squeeze with statler, testing and backports enabled
Background - Chrome has a built-in PDF viewer, but Chromium doesn't.
Finally managed to get PDFs to display in Chromium. Took a lot of messing about, but this worked for me. Debian's stable Chromium is still only at version 6. Enable testing and install the latest - currently version 20. Then download the latest Chrome for your system. We are going to extract the libpdf.so and install it into our system.
WARNING - Somewhere towards the end of this process root seems to have a habit of taking ownership of the folder you are working in. This is really bad if it is your /home/"your name" folder!! So copy your downloaded Chromium package to a new folder that can be thrown away at the end of the process.
So, in that folder su to root. Then extract the .deb with
# ar vx <previously downloaded .deb>
Then extract the data payload -
# tar --lzma -xvf data.tar.lzma
We then drill down to $WORKDIR/opt/google/chrome/libpdf.so ($WORKDIR being the folder you are working in) and copy it to /usr/lib/chromium - or at least that is where the chromium folder is on my system. You may need to check /opt if it's not in the /usr path.
Once this is done open Chromium and enter "about:plugins" in the address bar and it should be listed as "Chrome PDF Viewer". Open a PDF file to test.
At this point you may well find that the folder with the dismembered carcase of Chrome is now owned by root. Trash it. If you want to keep it su to root and do -
chown -Rv your_name path/of/folder
Anyway, it worked for me in the end, and doesn't need mozplugger or acroread, both of which can really pull in some stuff!!