By defualt Kubuntu with KDE4 (at least) sets up Print Screen to work with ksnapshot. This program grabs the screen (or a window with the -c option). The program is minimal and lets you save a file, copy it to the clipboard, or open it with a program.

However, you can use apt to install kgrab. This program is functionally the same as ksnapshot but it has an actual menu as well as a way to directly print screen shots.

However, both the KDE “input actions” and Compiz were trying to handle the print screen key. Changing ksnapshot to kgrab didn’t do anything! So the solution was simple:

cd /usr/lib/kde4/bin
sudo mv ksnapshot ksnapshot.orig
sudo ln -s kgrab ksnapshot

That does it.