To obtain this achievement you must take a photo of all 100 PP stickers in the store, you should progress into the game until you open up the entire entrance plaza because if you don't it will be inaccessable.
Warning: This achievement becomes unobtainable once you
1) Progress into the storyline to case 2-3, do not fail before then.
2) Kill Saun the Cult leader without getting captured and getting the 2 PP stickers in the room they take you to.
I also recommend (if you have not hit level 50 yet) to grab the PP photo books that increase the amount of XP you get from taking pictures which are in paradise plaza. Here's where they are:
-Camera 1: Contemporary Reading (+25% from photographs)
-Camera 2: Photographer's Pride (+100% from photographs) (only at the end of KENT's Storyline)
-Camera 3 is in the Entrance Plaza (+25% from photographs) (only once the entrance plaza is opened up)
Another tip I can recommend is to either grab a bicycle (one can be found in the Entrance plaza) and a skateboard or 2 from the 2nd floor of paradise plaza to help move around more quickly, the skateboard can only hit about 3 zombies, but if you grab both books you can hit 20+ zombies until it breaks so unless you have the books don't use it to get past zombies.
Here is a list of all locations (pulled from Howard Da Ninja
's solution from the 360 version):
Found a fantastic video on youtube of all locations done by youtube user Letsplay Community:
Lastly make sure to finish this game (you can be at the heliport pad when the timer counts all the way down) if you want the reward for collecting all PP stickers, a lovely hockey mask!