SKYHILL

On the 1st level, open the file in the computer to the left and enter the password:
mr.wgmthooh
The achievement will unlock once you exit the door of the hotel.

Notes are randonmly placed in a run, the game will always put up notes you havent found or read yet.
You cant get all notes in a single playthrough.
There are a total of 52 notes to get.
Because of the mechanics, you need to read the notes in your inventory as to remove the New tag or else, you wont get new notes.