I have written a post about how to install LibreOffice 4.0 via deb packages. In that post, you have to download deb packages from LibreOffice from its official website and then install them manually. Using that method is good if there is no such application on Ubuntu repository or PPA repository. Finally, LibreOffice 4.0 has been packaged and uploaded into LibreOffice PPA on Launchpad, so you can install LibreOffice easily and get the update when available.

In case, you haven't read the news about LibreOffice 4.0, I'll give a brief description about what's new in LibreOffice 4.0:
  • Mozilla Firefox personas support
  • Android remote control app for controlling presentation.
  • Ability to import Microsoft Visio and Publisher documents.
  • Allow extra word boundary characters
  • Import / export support for native RTF math expressions
  • Allow different header and footer on the first page without using a separate page style
  • More support for DOCX and RTF documents.
  • Much accelerated multimedia previews, and previews of embedded video on Linux
  • Include for new open source fonts Open Sans (Ascender), PT Serif (ParaType), Source Code Pro and Source Sans Pro (Adobe)
Or you can read the full changelog of LibreOffice 4.0 here.

Install LibreOffice 4.0 on Ubuntu via PPA
Ubuntu users can install LibreOffice 4.0 by adding the PPA below:
  • sudo add-apt-repository ppa:libreoffice/ppa
  • sudo apt-get update
  • sudo apt-get dist-upgrade
Now, please sit back and relax while package manager downloads and installs the latest version of LibreOffice for you.

Regards :)