What is the easiest way to update an existing LibreOffice installation that’s NOT from the distro’s repositories? For example, I used the .deb archives for my custom/minimal Ubuntu installation to install the 64-bit LibreOffice manually and now want to update it. The preferred or recommended way seems to uninstall all previous packages, download the new .deb archives and install them. Quite bothersome, to be honest.
Would a PPA work for your needs?
@Merc - Looks like you thought that a PPA would work (per an Answer you gave), but it now appears that your Answer has since been removed. Did you run into problems trying to use a PPA?
From Libreoffice3.5 onwards multiple versions can co-exist side by side. This is convenient for testing and migration. However, as each copy takes up about 548 mb on my system many users prefer to remove the older versions.
If you install manually say using dpkg -i *.deb, LibO is installed on my Ubuntu 12.04 system to /opt/libreoffice3.5 (3.6 4.0) etc depending on the version. Release 3.6.3 will overwrite 3.6.2, both using the same libreoffice3.6 folder.
This approach is slightly more effort than using vanilla Ubuntu but allows you to use whichever version of LibreOffice you choose. When finished with an older or testing version, you can simply remove it and save the space.
More information about installing multiple copies of LibreOffice side-by-side can be found here on the wiki: Installing several versions of LibreOffice in parallel - The Document Foundation Wiki