Layers of Fear (2016)

Here is a full video guide which will get you this achievement along with many of the other DLC achievements including the Tree and the apple ending.

I prefer text guides, so I used the solution provided by JUSTTHINKSD, which identifies the specific 23 collectibles that count toward this achievement and excludes all those that don't count. Then I watched the video and came up with this text-only solution.

MISCELLANEOUS ROOMS
1 - Entrance: "Dear Friend" note from lawyer J. J. Sadler at the front doorsill.

2 - Living Room: Certificate of Pedigree by the front window.

3 - Living Room: "My Beloved" note in a cabinet drawer next to the workshop.

4 - Bathroom: Hawaii brochure next to the commode.

5 - Basement: "Dear Mr. and Mrs. Kirkstein" note on a table to the left of the stairs, in a corner.

THE WORKSHOP
6 - Letter from publisher C. J. Marshall in the drawer below the drawings wall.

7 - Use the crayon next to the easel to enter the Land of Fables. Now Walk forward past the easel, pull the switch, follow the purple railroad path, grab the crayon, use it on the easel to draw birds and clouds. Now follow the green & yellow chicken foot path, go left at the Y, get stopped by the train, and make your way around the front of the train back to the other side of the crossing. Look at the drawing (angry dad at easel/happy mother and daughter in sunlight) resting against a lamppost.

8 - From #7, go back to the other side of the train crossing. Go back to the Y and take the right path. It gives out quickly and becomes dark. Keep going and you will see a red light. Look at the drawing reading "Your dad took it."

9 - Return to the easel. Use the paintbrush. Add the red paint (in the SW corner, if looking at the easel=North). Enter the narrow twisting corridor behind the easel and find the black paint by pushing a ball up a hill of toys. Add the black paint to the easel. Look to your right. Pick up the crayon. Look below it at the drawing of the princess dragging a sword.

Use the crayon on the easel to re-enter the Land of Fables.

NOTE: you'll be in the Land of Fables for a while, so go forward past the easel and pull the sword from the stone now. The next time the serpent comes by, you will slay him, removing that annoyance and earning you if you don't have it already.

10 - At the easel, turn around and follow the pawprint path. When you get to a lampost and a junction, go left down the leaves path. When you see a drawing of a blue flower on a yellow circle, RUN (hold ) toward the flower and get there before you're locked out. Look at the drawing of the girl at a grave.

11 - Return to the pawprint trail and follow it to the lamppost junction where you just were. Go right and find the treehouse. Climb the ladder, go in, and wait for the cutscene to end. Pick up the crayon. Return to the easel and draw three lollipops. You're going to follow the pawprint trail again, but things are flipped, so it isn't where it was. Go to the junction you've been to twice already and look the drawing reading "I told him nothing."

12 - From #11, go left down the leaves trail. Look at the drawing of the dog with a heart between two halves of his body.

13 - From #11 again (the junction), take the shoeprint/pawprint path. Look for a horse on the ground and look at the "Why Pink" drawing.

14 - From the easel, go left down the light-colored path that passes by some cups and saucers. When you get to some standing crayons, look at the drawing of the girl and a menacing black figure.

Now you can leave the Land of Fables any way you want to. The quickest is to take the green and yellow claw path to the jack-in-the-box, get his crayon, and use it. (There will be another drawing you can look at in the workshop, but it doesn't count for this achievement.)

If the vision started before you got #6, get it now.

THE OFFICE
15 - The distorted sheet music on the piano.

16 - In the room with the broken furniture, make stairs out of the chest of drawers, climb it, and touch the clock. Turn around and look at the table. When there are bottles and books stacked on it, step off. Look for a drawing reading "Get Well Soon" sticking out of the books by the fireplace.

17 - Touch the clock again. When you see a candelabra and a red plant on the table (and not a gramophone), step off. Look at the "Dont be sad Momy" drawing on the seat of the wheelchair.

18 - "What time is it?" card inside the toybox with a large X inside the lid.

19 - After you collect the third piece of the drawing of the mother, go DOWNstairs to a basement. Turn left and make your way to the end of a narrow, winding passage. Look at the photo of the girl and dog.

20 - Knock the red vase over and grab the key. Open the door as if you're going to leave the room, but don't. Go back and open the small cabinet to the left, unlock and open the chest, and look at the drawing of two dogs.

21 - "A Glimpse Into the Future" clipping behind the first board ramp.

22 - "Mising Cat" drawing in the toy room next to the Mr Scooter room.

23 - When the vision ends, look at the Last Will and Testament in a right-hand desk drawer.

There are 23 notes totally.Outside the vision,in the real world,only 7 notes count(not like the walkthrough listed the henry marvin card don't count),the 9 kid drawings and the items DON'T count.In the crayon vision,there are 7 kid drawings which is count and 1 in paint brush vision which is count.In the mom/dad vision only 8 paper stuff count.by the way the code paper and the last kid drawing near the lose-wheel-cat don't count.

check this video:

this guy collect all stuff even which is not count so use this video and my list to check which you lost:

1 1:04
2 1:15
3 1:47
4 2:23
5 2:39
6 3:26
7 4:00
8 4:35
9 5:01
10 5:32
11 5:47
12 6:04
13 6:31
14 6:51
15 9:08
16 9:49
17 10:33
18 12:03
19 12:46
20 13:25
21 13:32
22 14:53
23 15:51

After needing 2.5 playthroughs to earn all DLC achievements, here are some tips to hopefully help gamers finish in two runs. Since I finished the main game in one run with only chapter replays needed (my tips are under the Omniscent achievement); I think multiple replays can be shortened for the DLC. There are no 'chapter replays' in the DLC. And your game may place or hide collectibles differently from my game or any guide available. If you are absolutely sure you have every document, you can skip most of the crayon world by using the paintbrush. This collectible achievement will unlock as soon as you have all collectibles, no matter where you are at in your playthrough(s). Be sure to push the extra key on screen to zoom & read notes. You can start any flashback first where you believe you are missing a collectible. This achievement is NOT earned by solely reading notes.

Potential Spoilers Please play Inheritance once so you will understand these tips.

1). Use the excellent TA guide for your first run. Many thanks, authors!
2). Alternate following parental path on second run.
3).If you do not get the 'This Could Be Important' achievement on your first run, check the You-Tube video by rus199410 Thank-you, rus.

Mistakes I made: Turned the crayon world upside down (by climbing the ladder) before I found all collectibles, missed the mousetrap in the closet and failed to switch parent paths by following the Father portrait x2 vs switching to Mother portrait (in my run there was a picture only available in the clock room on her side). Failed to hold the flashlight 30-60 seconds on solved portrait puzzle, then failed to turn flashlight off and wait for map to appear to cue up the shelves to earn The Tree and The Apple achievement. Did not rotate items to check for rotation viewing/writing on back, i.e.- the red paint can in the chest in the workroom/paint room and the Dr. name card in Father's desk. In the clock room check every room change available BEFORE opening the safe.

Good luck and my thanks to the many gamers who have posted their problems & successes. They helped me get where I wanted to go. That's why I am posting this, as some will play this based on getting the main game, Layers of Fear recently FREE on XBOX gold.