I'm trying a primaris playthrough right now and I'm a little confused about the apothecary situation. I've researched and manufactured a set of MKX Apothecary armor, but none of my marines can equip it. I I can confirm it's in the bases stores, but the only option I have when armoring my marines is the default MKX Tacticus armor, no option to equip the apothecary armor at all.
Edit: I've just found out I can equip it to my sergeant, which makes sense given an apothecary is an officer rather than a role a random marine can take. Probably should be noted in the pedia though.