In a gesture of anniversary goodwill (it’s been one year since the game launched,) Respawn have made the Titanfall season pass free on PC. If you want it, head over to the requisite Origin page and add it to your cart for zero pounds, dollars or euros.
“Thanks again to all of you who’ve supported us and we can’t wait to make more games for you in the future,” say Respawn’s Vince Zampella in a post on the game’s official site. “In the meantime, if you haven’t tried the new maps, we hope you love them and happy anniversary, Titanfall!”
To actually make use of the season pass, it is, unsurprisingly, necessary for you to own the main Titanfall game. I think you can “buy” it even if you don’t own the game, though. In case you just want to store it for later, or something.
The season pass includes a triplicate of map packs, including Expedition, Frontier’s Edge and IMC Rising. Everything on this page, basically.