The blueprints are scattered through the map and somewhat hidden. To find them, have this in mind: This game has a lot of stuff outside its main path. So even if you are not explicitly told to go somewhere that doesn't mean you can't explore. There is more to discover than just what Marie tells you to do.
Also, interact with everything, the map props won't be highlighted as the items do but much of them can be interacted with.
And most over, have fun!