Blueprints are required to construct the various modules that can be assembled together to form a functioning station.
Blueprints are also required if you intend to use XL ships to supply subordinates. e.g. Missiles and Torpedo's for ships in a Fleet.
Players that have successfully logged into the Egosoft online system should obtain Venture Blueprints automatically.
Obtaining via Faction Representatives
The player may purchase Blueprints from the six factions in the game. Note that some Blueprints require certain licenses, which can be obtained by completing the promotion missions offered by friendly factions.
The complete list of where to purchase the Blueprints can be found here.
Obtaining via Data Leak Scans
This requires that you have certain Player HQ Researches completed.