Ubuntu – Which font formats can I use

First download fonts.

Then open Nautilus as root using the command: gksudo nautilus or sudo -H nautilus

Now copy your font file to /usr/share/fonts.

You can also paste it in /usr/share/fonts/truetype/ubuntu-font-family

(Type ctrl+L to navigate quickly)

Now you can easily use those fonts In LibreOffice.

This is a one-liner in a terminal. Open a terminal with Ctr+Alt+T and run the commands below. Replace <your_font_zips> with the folder name, where you have placed your zip font files.

cd <your_font_zips>
# next command extracts all TTF and OTF files into your `.fonts` folder.
unzip "*.zip" "*.ttf" "*.otf" -d ${HOME}/.fonts
# next command rebuilds font cache
sudo fc-cache -f -v

If you want to remove the fonts again, then simply delete the TTF files in your .fonts folder and rebuild the font cache.

More about fonts and Ubuntu here.

And yes, you need all TTF files.

TTF and/or OTF

I quote:

OTF is more likely to be a “better” font, as it supports more advanced typesetting features (smallcaps, alternates, ligatures and so on actually inside the font rather than in fiddly separate expert set fonts). It can also contain either spline (TTF-style) or Bezier (PostScript Type 1-style) curves, so hopefully you're getting the shapes the font was originally designed in and not a potentially-poorer-quality conversion.

_Source