In this chapter of the Metro Exodus Two Colonels guide, you will find locations of all the diary pages in this expansion.
First page - Foreman's Diary 1
The first note is found at the beginning of the expansion. As soon as you get the flamethrower, burn the tissue and go down to the desk with the diary page.
Second page - Foreman's Diary 2
When you turn on the water valve and go up the ladder, you will reach the first workbench. Inside you will find a slightly open door - go through it to reach the room with the note.
Third page - Worker's Note
When you get to the second crafting table, go down the stairs. The third note is on the left.
Fourth page - Trader's Note
Arrive at the celebration of the New Year, talk with the General and then go upstairs. Walk past the bar - the note is on the locker to the left of the bartender.
Fifth page - Letter
The fifth note can be received immediately after making a moral choice with the medication. The note is on the table.
Sixth page - Investigation Report
The sixth note is on the table - the part where you pass infected people.
Seventh page - Stalker's Diary 1
The seventh note is at the beginning of the bunker. You will get to it after a long cut-scene - the note is lying next to the destroyed locker.
Eighth page - Stalker's Diary 2
After restoring power, follow the arrows on the walls. You reach a room with a note (you will also hear the noise of the battle).
Ninth page - Stalker's Diary 3
The ninth note can be found right after the blind beast throws you down the elevator. Enter the ventilation shaft, the last note is at the beginning of it.