This trophy will pop soon as you complete all levels up and till 'Amendment XXV' under the game's hardest difficulty (Professional). In doing so you will also unlock Rookie Mode Complete, Normal Mode Complete and Expert Mode Complete. See the Hitman Blood Money - Professional Guide for how to complete the game under this difficulty. Throughout the 4 difficulties there are 5 variations between them:
Saves: When playing on Rookie difficulty you will get an infinite amount of saves, on Normal you will get 7, on Expert you will get 2 and on Professional you get none. Note: If you choose to use an in-level save, then you can not simply quit out of the game completely and then comeback, reload to place where you originally saved in the level. The in-game save system only works if you die, then you can reload and be returned to the place where you last saved.
Health: In terms of how much health you get under each difficulty, it is equal. When playing the game under Professional Difficulty, if you get shot at then you will incur a greater loss of health than you would do if you were playing on Rookie Difficulty. It is hard to quantify the difference between the four difficulties because of the variety of weapons. Some are more effective than others but on Rookie you can sustain approx 15 bullets hits before you die. On Professional it is around 5 hits before you are in serious trouble but bear in mind some guns are stronger than others. Finally, health does not regenerate.
Maps: On Expert difficulty you have a limited version of the in-game map, you will be able to see where everyone is but there will be no colour differentiation as they will be represented in a greyish colour. On Professional it will be even more limited as you will only see the targets, exit points and ICA Boxes. On Rookie and Normal you can pretty much see everything.
Notoriety: Notoriety is switched off when you play on Rookie difficulty but it is active on the 3 other difficulties, the harder the difficulty the more punishing your notoriety will rise if you have your cover blown etc.
Sound of Gunfire: If you fire a gun on the easier difficulties, the sound of your gunfire will fall on the death ears. On Professional, guards and civilians can hear your gunfire from several rooms away. Furthermore the Upgrade 1 Silencer for your weapons will not completely drown out the sound if you are playing under Professional.