Taken from "Webb's" achievement guide
I have now edited to show what part of the chapter they relate to.
Episode 1
1. (Waking up to a nightmare)
68th Annual Deerfest Sign – In the garage shop at the end of the level.
Episode 2
2. (Taken)
“Have You Seen This Man” – Wanted sign on a bulletin board in the police station by Sarah Breaker's office.
3. (Elderwood National Park)
The skeleton of a Columbian Mammoth – inside the lobby of the Elderwood National Park Visitor’s Centre.
4. (Elderwood National Park)
(The Moonshine Cave - After passing down the second set of stairs and over the bridge on the nature trail of Elderwood Park, instead of following the path to Lover’s Peak, follow the boardwalk around to the Moonshine Cave. Inside there will be a Moonshine Cave sign.
5. (Elderwood National Park)
After crossing the second bridge on the way to Lover’s Peak, follow the path to Lover’s Peak and there will be a sign in front of a huge tree with a hole in it. Stick to the path and you won’t miss it.
6. (Elderwood National Park)
The Tree Cut - After the third bridge in Episode 2, on the way to Lover’s Peak, after going under a small passage way called the “Through Tree”, bear right down the path towards a tree cut and read the sign.
Episode 3
7. (Mirror Peak)
The Bright Falls Coal Mine – Mid-way through episode 3, outside the main entrance to the mine, there is a sign on the left. More mining signs – right next door to #7. (doesn’t count though)
8. (Mirror Peak)
“Gray Peak Gorge” – After the graveyard in episode 3, which is after the coal mine, the train yard, and in a place Alan calls a ghost town. Just over the bridge.
9. (Mirror Peak)
“Cauldron Lake” – After the silver mine, passing over the valley on the cable cart and by a safe haven up the hill. Can’t really miss this one.
Episode 4
10. (The Truth)
A huge sun dial on the balcony when you’re walking with Hartman. “Beyond the shadow...” reads the poem on it.
11. (The Truth)
“The Creator’s Dilemma” – a poster by the main entrance to the lodge. After going inside after sign #10.
12. (The Truth)
“Welcome to Cauldron Lake Lodge” – After following Hartman through the passage after exiting the main lobby area of the lodge, on the right wall there is this sign.
13. (The Truth)
After leaving the lodge interior and making it into the courtyard, there is a statue as a centre-piece there, read the sign. It reads, “Suspended, Lauren Miller, 1989.”
14. (The Anderson Farm)
The Old Gods of Asgard – A poster on the wall in the Anderson’s barn (after the stage defence), past the button to release the Viking boat as a battering ram.
Episode 5
15. (The Clicker)
After seeing Barry, you’ll run through a small park with benches and a statue of two hunters and a deer in the middle. Read the statue’s sign.
16. (The Clicker)
Alex Casey advert on the wall next to the table in the ground floor of the bookstore.
17. (The Clicker)
After the bookstore and the children’s playground, you’ll come across a church with a sign out front. Read it.
18. (Bright Falls Light & Power)
Before pressing the button to move the bridge – the rotating one – there is a sign on the right side of the road (nearest where you come from, set back slightly) – it reads, “Lt. William TG Randall Memorial Bridge.”
19. (Bright Falls Light & Power)
Outside the doors to where you talk to Weaver – “WARNING – this decommissioned site...”
20. (Bright Falls Light & Power)
“Floodgate controls” sign – where the... you guessed it, floodgates are – can’t miss it, there is a series of three buttons there.
21. (Bright Falls Light & Power)
When you have to hold the door open for Barry and Sheriff Breaker, there is a “NOTICE” to the right of the button – after you exit the elevator.
Episode 6
22. (Departure)
After getting in the car and driving across the bridge to the first roadside opening, with cars, benches and toilets, there is a huge sign there for the “Majestic Hotel.”
23. (Departure)
Actually at the Majestic (night time scene), there is a general information board in the lobby.
24. (Departure)
After the second tunnel, where the road is blockaded and you have to go right up a dirt path, there is a sign on the gate before you enter with opening and closing times.
25. (Departure)
When you veer off after the second tunnel on to the dirt road, before you open the gate. Before entering the building that has a “Larsen’s” and a “Auto Salvage and Used Parts” sign on top of it, there is a sign on the left of the door to get in.