Edit: Due to the fact that this article is old, the installation instructions may not work anymore. In order to successfully install the latest version of KDE Plasma, please access the KDE tag and open the latest article (the one on top).

The latest installation instructions for KDE Plasma
Hello Linux Geeksters. As you may know, KDE 4.13.2 has been released last week, coming with about 40 bug-fixes and improvements for some applications, including: , Kopete, Dolphin, Konqueror, Kontact, Umbrello UML Modeller and the Desktop search functionality application. For a full list of changes brought by KDE 4.13.2, see the release notes.
While KDE 4.13.2 was available in the KDE Backports PPA only for Kubuntu 14.04, now the needed binaries for Kubuntu 12.04 have been also added to the same PPA.
In this article I will show you how to install KDE 4.13.2 on Kubuntu 14.04 Trusty Tahr and Kubuntu 12.04 Precise Pangolin.
Because it is available via the Kubuntu PPA, installing KDE 4.13.2 on Kubuntu 14.04 and Kubuntu 12.04 is easy. All you have to do is add the ppa to your system, update the local repository index and perform a full system upgrade:
$ sudo add-apt-repository ppa:kubuntu-ppa/ppa
$ sudo apt-get update
$ sudo apt-get dist-upgrade
If you don’t have a previous version of KDE installed on your Kubuntu 14.04 or Kubuntu 12.04 system, do:
$ sudo add-apt-repository ppa:kubuntu-ppa/ppa
$ sudo apt-get update
$ sudo apt-get install kde-standard kubuntu-desktop