Official add-ons

The official add-ons are pwads that can be downloaded from Bethesda.net to be played with Doom Classic Unity port. Since console manufacturers do not usually allow players to use third-party content, the official add-ons system allows a selection of mods to be downloaded and played instead of being limited to the IWADs. Official add-ons are curated to ensure they are playable within the (raised) limits of Doom Classic, and to avoid potential copyright infringement in their content. Also, the consent of all original authors is mandatory, according to a Doomworld forums by id Software member Mike Rubits (sponge) so that they all have to be contactable by id Software in order to license their pwads.

List of official add-ons
The two Final Doom IWADs are available as official add-ons for both The Ultimate Doom and Doom II. This effectively makes Final Doom free for all owners of either Classic Doom titles on Bethesda.net.
 * The Plutonia Experiment
 * TNT: Evilution

Ultimate Doom

 * Double Impact
 * SIGIL

Doom II

 * No Rest for the Living