Packages for the release of KDE SC 4.9.1 are available for Kubuntu 12.04 and 12.04.1 LTS releases. You can get them from the Kubuntu Backports PPA. They are also in our 12.10 development release.
To update, use the Software Repository Guide to add the following repository to your software sources list:
Or, from your konsole:
sudo add-apt-repository ppa:kubuntu-ppa/backports