On Ubuntu 16.04 and Ubuntu 18
sudo apt-get install python3-minimal -y sudo apt-get install graphviz -y sudo apt-get install ghostscript -y sudo apt-get install du -y sudo apt-get install aspell -y sudo apt-get install dot -y sudo apt-get install unoconv -y
Source Moodle Doc: https://docs.moodle.org/35/en/Universal_Office_Converter_(unoconv)
Bash Script:
https://github.com/devlionco/bashscripts/blob/master/install_unoconv_moodle_ubunut_18.sh