Packages for the release of KDE SC 4.9.3 are available for Kubuntu 12.04, 12.10 and Raring. You can get them from the Kubuntu Backports PPA for 12.04 and from the Kubuntu Updates PPA for 12.10. Raring testers will get it with the regular updates.
To update, use the Software Repository Guide to add the following repository to your software sources list:
12.10:Or, from your konsole: