This page of The Last of Us game guide contains information on where to find the comic books in the Pittsburgh chapter. Those items are collectibles-secrets. Our walkthrough indicates the exact location of each artifact and pendant.
Comics #1 - Force Carrier
You will receive it automatically after you begin this chapter.
Comics #2 - Termination Shock
After you jump out of the bandits' place, you will e going by a bus.
The comic is inside the bus.
Comic #3 - Accretion
At some point you will be rescued by Ellie who will kill the bandit strangling Joel. Afterwards, climb up the ladder and turn to the left.
To the left, you will be passing by a collapsed floor.
Slip past the hole and pick up the comic from one of the tables.
Comic #4 - Deep Phase
After you meet up with Henry and his brother, go downstairs and open the locked door with your knife.
There is a flat behind the door. In the child's room, there is the comic on the chair.