That's where I am right now. I wanted to try the
-DWITH_PDF=ON to see what
additional functionality that provided. I don't know for sure, but I think
it might be used for pdf thumbnailing or other ancillary pdf processing
functions. The current kpdf works great with kdegraphics built without
-DWITH_PDF=ON, so I'm not driving myself crazy over it (I've already done
that long ago :)
However - what sucks is I'm the poppler-qt3 maintainer for AUR, but I'm NOT
the AUR maintainer of Qt3 - issues.....
Here we go.
1) yes it is the thumbnailing plugin that it is used for, nothing
else, unfortunately if you disable it, you loose all of your
kfile-plugins.
2) make your own package, like trinity-qt3 ( i think i own that one,
but you can have it) that way you can muck around with it, and give it
what we need.