Debian Wheezy ships with Libreoffice 3.5.4 out of the box. However the newest version 4.0.3 offers numerous improvements over the previous version such as improved start up time etc.
Fortunately wheezy backports offer a way to install version 4.0.3 without “upgrading” your installation from stable to testing or even unstable.
Add the backports repository on Debian Wheezy:
$ sudo su
# echo 'deb http://ftp.debian.org/debian/ wheezy-backports main contrib non-free' >> /etc/apt/sources.list
# echo 'deb-src http://ftp.debian.org/debian/ wheezy-backports main contrib non-free' >> /etc/apt/sources.list
Update package information:
# apt-get update
Install LibreOffice from backports repository
# apt-get -t wheezy-backports install libreoffice