http://projects.gnome.org/evince/
http://kpdf.kde.org/
http://okular.kde.org/
http://www.foolabs.com/xpdf/

I think the first stage should be quite easy for a medium skilled programmer.
However respecting "maemo conventions" eg. single click only - no double tap needs some tinkering.

As I'm not really into pdf I suggest anyone who is interested should check the projects above and form an opinion.

Please consider adding other open source projects if you know any so that we may start a thread in applications on this matter.

Thanks