Where to find the map to display all 8 documents in Cold Darkness:
Make sure you have this challenge selected when you are setting up the game or you won't get the achievement. I have tested this numerous times and the documents and the map are not random.
Couple of notes before you read the next paragraph. The main objectives are not "guard towers". They are also not small squares right next to the large facility in the middle... so therefore, I am not talking about the towers that you have to shut down. Sorry I had to explain that!
Looking at the map there is a 9-sided giant facility right in the middle. North are the trains and basically to the East, South and West in very close proximity are 3 guard towers, 3 small squares on the map. Go to the Eastern guard tower. It is south eastern, I say east because I am talking in relation to the other guard towers and the trains which are right next to the big facility in the middle. This gives you an idea of how close it is. So look at the 3 dots that are not north and right next to the big facility. They are all pretty much the same distance away from the big facility in the middle. The one on the right which is between the giant 9-sided facility and a decent sized area of black (off limits I guess), that is where your map is!
Where Lara is on the map is right next to the tower with the map. I made a better picture that circled the tower and the tree to climb up for one of the collectibles but I can't figure out how to get TA to let me upload or paste it so until then this will have to do!
Omega Doom has mentioned that it is hard to get to. He found it was easiest to find coming from the west side. It is possible to get to from the east but some places you can only cross via fallen tree trunks.
In revisiting myself I found that if you struggle to get there you can go from the Southern objective tower and head north, you will see 2 concrete walls sloping up towards the giant facility, Find the walls and climb up some boxes to the right and you should be pretty much right there.
The collectible that is just to the north of the giant 9-sided facility in the middle may be a pain to figure out how to get to. It's very high up. The way I got up was to climb up some trees to the North-West (left) of the platform that the document is on. You should be able to see a rope going up from the tree to another platform that is right next to where you want to go. That is a fixed rope that is already there, not one you place yourself! When you climb up the trees and are sitting right beneath the rope you want to climb the game may trick you into thinking you can't climb it (I fell down a few times) but have another go you can climb the rope up to the large platform that the document is on.
CR Trooper 014 added a link in the comments to a youtube video if you prefer that.