Easy "I know everything" Achie...
	Easy "Maintenance key" Achieve...
	Various Steam Achievements...

Twenty five of the notes are easily found as the storyline progresses by just selecting everything. The remaining two notes are as follows.

There is a note that can be found in the attic near the start of the game. Do not use the "5543" password before going to attic, or forgetting to go back in if you die.

Exhaust the dialogue with the homeless man.

Exhaust all the dialogue options with the homeless man found near the sewers.

Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Bad Ending	You've unlocked the bad ending.
First time	You've unlocked your first note.
I know everything	You've unlocked 27 notes.
I made it!	You've unlocked the good ending.
Maintenance key	You have found the key to the maintenance room.