Finally LibreOffice  got a PPA which now makes it very easier to install and stay up to date with the latest LibreOffice versions. LibreOffice 3.3 has come up with new exciting features  import and bundled extensions which provide PDF import, a slide-sow presenter console and more services. It also works with SVG files. Follow these steps to install LibreOfiice 3.x via apt-get install :
Remove OpenOffice from your system
sudo apt-get remove openoffice*.*
Add LibreOffice PPA - Lauchpad Repository
this repository can be use in Ubuntu 10.04 Lucid Lynx, 10.10 Maverick Meerkat and 11.04 Natty Narwhal:
sudo add-apt-repository ppa:libreoffice/ppa
sudo apt-get update
Install LibreOffice use following command
sudo apt-get install libreoffice
To get better compatibility with your desktop environment, also install following package
Install LibreOffice for Gnome
 sudo apt-get install libreoffice-gnome
Install LibreOffice for KDE:
sudo apt-get install libreoffice-kde
in addition, while removing OpenOffice, the spellchecker and the language support package are also removed. You can get these packages back by installing the following package. You can replace “-en” with your language in the above command.
sudo apt-get install language-support-en
source : www.webupd8.org