I tried installing the PCLOS version of Voikko and after having tried to get it working in OOo for over an hour I'm coming to the conclusion that pinoc is right: it is a pain.
I did manage to run the spellchecker from the commandline -- checking the spelling of one word at a time, which I didn't find very useful. And no luck with OOo.
One reason might be that there's no package like Mandriva's "openoffice.org-voikko" in the PCLOS repos: at least this package contains an .oxt file that the PCLOS packages lack.
I did, however, find something more ominous in an answer to a question in the Finnish FAQ: The question was "How do I install Voikko in version 2.x or 3.x of OpenOffice.org under Linux?
", and part of the answer was:
Unfortunately OpenOffice.org does not make it possible to specify the interdependencies between extensions (openoffice.org-voikko) and external components (libvoikko). They can only be defined through a Linux distribution's own package-management system, and consequently Voikko can only be used together with a version of OpenOffice.org that comes from the official sources of the distribution. In this respect Voikko is fundamentally different from the earlier closed-source spellchecker Soikko: Voikko is a spellchecking component that comes with the operating system, Soikko had to be installed separately for every application.
(I translated the above almost word for word without aspiring for elegance, because while I seemed to understand what I was translating I still don't know what it means in practice.)
I'd also like to add that the Finnish documentation is mainly about linguistics and the algorithms used in "libvoikko". It actually says less about installing Voikko than the English "Quick installation instructions".
Edit: corrected punctuation.