Packages for the release of KDE SC 4.12 are available for Kubuntu 12.04LTS, 13.10 and our development release. You can get them from the Kubuntu Backports PPA.
Bugs in the packaging should be reported to kubuntu-ppa on Launchpad. Bugs in the software to KDE.
To update, use the Software Repository Guide to add the following repository to your software sources list:
12.04LTS, 13.10:
ppa:kubuntu-ppa/backports
Or, from your konsole:
sudo add-apt-repository ppa:kubuntu-ppa/backports