LibreOffice 4 on Fedora 18...

It seems that LibreOffice 4 won't be packaged for Fedora 18, only in Fedora 19 judging from the fact that it is already in Rawhide and in previous versions of Fedora only minor updates were performed. So, if you need some feature from this newer version you'll have to install it separately from Fedora's repositories. Fortunately, it isn't so hard and/or dangerous to do and here is how.

First, go to LibreOffice Download pages and click on the Main installer link. This will trigger download of archive with all the RPMS necessary for the installation. Note that it's cca. 180MB of data.

After the download finishes, unpack it and you'll have a new directory LibreOffice_4.0.0.3_Linux_x86-64_rpm. Enter that directory, then RPMS/ subdirectory and finally run the following command (as a root user):

yum localinstall *.rpm

When asked to confirm installation process, just hit y. Additionally, install package that will provide LibreOffice 4 in different GNOME menus (note: this is a single line):

yum localinstall desktop-integration/libreoffice4.0-freedesktop-menus-4.0.0-103.noarch.rpm

Now, you can run LibreOffice 4 like you would run older LibreOffice. Note that you have both versions installed in parallel.