Remove the screws from the interior face plate of your deadbolt lock with a screwdriver. Remove the lock tumbler by pulling out on both sides. Remove the screws in the face plate around the bolt on the edge of the door and pull the bolt from the door.
Replace the 1 to 1/4-inch standard bolt with a long throw deadbolt, available at your local hardware store. Insert the new bolt, replace the screws in the plate on the edge of the door, insert the two halves of the tumbler through the hole in the bolt and thread the mounting screws. Tighten them with a screwdriver.
Remove the bolt receiver plate on the opposite door, across from the deadbolt. Use a 1-inch paddle bit to deepen the bolt receiver hole to 2 1/4 inches. Add a brass reinforcement receiver bracket over the edge of the door to reinforce the 2 inches on either side of the bolt and cover the gap to prevent prying the bolt. Attach it to the door's edge with screws provided with the bracket.
Set a barrel bolt latch 3 inches from the knob edge at the bottom of the passage door. The stationary door probably already has a small one. Choose a 1/4-inch bolt at least a 3/4-inches long. Mark the screw holes from the bolt bracket onto the face of the door and drill a 1/4-inch deep pilot hole in each spot with a 1/8-inch bit. Drive the screws in with a screwdriver to attach the bolt to the door face.
Mark the end of the bolt on the floor where it hits to position the receiving hole. Drill a 3/4-inch deep hole with a 5/16-inch bit. Drop the bolt into the hole and turn it to the latched position. Test the deadbolt to make sure the placement is accurate, file the edge of the hole with a round rasp if needed to allow the deadbolt to open and close smoothly.
Add a second barrel bolt at the top of the passage door in the same way, add a top barrel bolt to the stationary door if it doesn't already have one, using the same procedure.
Replace the screws on the jamb side of the hinges on both doors with 3-inch treated deck screws to anchor the hinges to the frame behind the jamb. Run the screws in flush, and do not over-tighten.