Outlast

This achievement is missable.

There are a total of 13 documents and 18 recordings, making up 31 collectibles overall. As with the main game, documents are the flashing blue folders that must be picked up, and recordings are significant events you must record with the camcorder.

Remember, you must collect all the documents or recordings in one playthrough. Collectibles do not carry over between multiple playthroughs, and using chapter select resets your progress.

Glitch Notice: Many players have reported that pressing the guide button while playing resets your collectible progress, so make manual saves often and avoid touching the guide button when going for the collectibles. Once you’re done playing for the day and you’re still in the middle of collecting, make a save and quit to the main menu. From the main menu you can press the guide button and your collectible progress shouldn't reset.

Wozamil from PlayStation Trophies created a wonderful video guide which covers every single collectible, so big thanks to him! Feel free to watch the video for assistance.