In Dishonored, Blueprints are available for Corvo to unlock throughout the the entirety of the game. Each of these special upgrades must first be found within the game world and delivered to Piero, whom you can find at The Hound Pits—the central location in the game which you return to after each mission.
You'll have the opportunity to find each of these upgrades twice, so should you miss them the first time around, you'll have a second chance to claim them. Additionally, level 2 of the Dark Vision ability will highlight these blueprints in green to make them easier to find.
Note: the pictures below are unrelated.
Lens Magnification (Vision Upgrade)
Option 1: First, save Griff from his attackers near John Clavering Blvd. and Bottle Street early in the mission to assassinate High Overseer Campbell. Doing so will gain you access to his store, where he stocks the Lens Magnification and Sokolov's Formula blueprints.
Option 2: Should you miss the blueprints the first time around, you'll have the option to pick them up when you visit Griff in mission afterwards. Remember to stock some coin before heading off to the mission, or pilfer some gold from a few guards and citizens.
Option 1: Save Griff from his attackers during the mission "High Overseer Campbell", and he'll have the blueprint for Sokolov's Formula in stock for you to purchase in addition to the aforementioned Lens Magnification blueprints.
Option 2: The blueprints can also be found inside Sokolov's mansion in the mission "The Royal Physician". The blueprints are in the greenhouse at the top of his laboratory.
Bonded Galvani Weave (Armor Upgrade)
Option 1: You can find this blueprint in a locked chest located in the Overseer's Workshop. The workshop is located behind the Overseer's Mansion area in the mission "High Overseer Campbell". The key to the chest is inside a glass bottle on a shelf in the corner of the workshop.
Option 2: If you miss it the first time around, you can find the blueprints in Daud's office later in the mission called "The Flooded District". Be sure to grab his key before you gain access to the office.
Option 1: The blueprints for Incandescent Paste can be found in the Dunwall Whisky Distillery during the mission "House of Pleasure". Look for a valve wheel which operates a fast-closing shutter and you'll find the plans stored in one of the lockers. Simply use your Blink ability or slide under the shutter before it closes.
Option 2: During the mission "The Flooded District", head down to the cellar near the exit of the Gateward Tunnel location.
Folded Galvani Resin (Stealth Upgrade)
Option 1: The blueprints for the Folded Galvani Resin are located in the first warehouse in "The Royal Physician" mission. There is a wagon inside the warehouse you're looking for.
Option 2: Like the armor upgrade, these blueprints can be found in Daud's chest during the mission "The Flooded District".
Option 1: This upgrade allows you to fire explosive bullets. You can find the blueprints in Dunwall Tower during the mission "Return to the Tower". It hides in the general's office on the second floor.
Option 2: The blueprints can also be found in a wrecked railcar at the Central Rudshore Red Line Station during the mission "The Flooded District".
Spiked Grenade Housing (Grenade Upgrade)
Option 1: These blueprints will allow you to equip yourself with sticky grenades. You can find them in the mission "Lady Boyle's Last Party" inside the guard post by the entry point to her mansion. The blueprints are on a desk.
Option 2: During the mission "The Flooded District", the blueprints can be found in a partially destroyed corridor in the building full of thugs. It's kind of a bitch to describe, so you're better off finding them in the Lady Boyle mission.