The Two Colonels DLC in Metro Exodus has 9 diary pages to collect. If you obtain all 9 diary pages, you will receive The Whole Picture Trophy/Achievement. Below is a listing of the locations for all the diary pages. You will need to collect them in this order, since you can get locked out of areas as you progress through the story.
Foreman’s Diary 1
When you first gain control, head down the stairs and proceed forward through the hallway, burning the slime as you go. At the end of the hallway, turn right and head through an open doorway to find the diary on a metal table straight ahead.
Foreman’s Diary 2
When you reach the room with the first workbench and a generator, take the door to the right of the workbench and follow the hallway to reach a storage room containing the diary on a green metal shelf next to a table containing large boxes.
Worker’s Note
Starting at the second workbench (accessed by going through a hole in a bathroom wall), head through the door leading to a hallway and follow the hallway to the end. Once at the end of the hallway, kick open the door on the right side and head through it onto a metal walkway. Take the first left to find the diary sitting on a metal console.
Trader’s Note
After you speak with the General, you’ll head home to your son. On the way, you’ll pass through a bar. The note is located to the left of the bar on a shelf.
Letter
After you leave Petrovich’s house, head to the table across the way on the other side of the railing. The diary will be located on this table next to a scale.
Investigation Report
When you take control of the Colonel during the rioting, exit the armory with the workbench and head right down the hallway to enter the med bay. The diary will be located on a table under a lit lamp just before the door the soldiers opened for you.
Stalker’s Diary 1
When you gain control of the Colonel after the cutscene where everyone was gassed, head down the concrete stairs to enter a shower room. The diary will be located on the ground.
Stalker’s Diary 2
After fending off the hordes of enemies in the big, open, garage-like room, head through the newly opened giant metal door. Take a right and head through a doorway to enter a stairwell. Descend down the stairs to reach a room with three sets of elevator doors (all marked with an “X”. Take a left, passing through a giant doorway, followed by a right through an open door. Head down the flight of stairs to arrive in a flooded room. Turn left and make your way through this room then head up the flight of stairs. Turn right to find the diary on a metal table.
Stalker’s Diary 3
After fighting the Blind One and falling down the elevator shaft, you’ll find yourself in a dark room filled with metal scrap. Head up a metal frame of the drop ceiling towards the yellow light to find the diary on a concrete ledge next to some tubing.