Paradox has made has made Europa Universalis IV free at the Epic Games store for one week for it’s 10 year birthday, until August 17. As with other free games it will stay in your library after the date is over and you will be able to play it in the future. Download it here.
A range of DLCs are also on sale (not all, but the majority), between 20 to 50% down. Check them out here.