The Tex Live included in Ubuntu 12.04 is version 2009. It’s very old so that if you would like to install the latest version 2012 you can use TeX Live backports ppa to backport the latest TeX Live from Ubuntu 12.10 “Quantal Quetzal” Alpha to Ubuntu 12.04 LTS.
Open terminal and addvia this command:
sudo add-apt-repository ppa:texlive-backports/ppa
Update the source:
sudo apt-get update
Now install tex live 2012 with this command:
sudo apt-get install texlive
Or launch Synaptic Package Manager, search and install/upgrade Tex Live packages.