Activating this trainer
If not state otherwise below, press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.

Promo Options
NumPad1: Unlimited Items/Ammo/Arrows

Trainer Options
# Items 
     NumPad1: Unlimited Items/Ammo/Arrows

Editor Options
# Player Stats 
     Current Health
     Max Health
     Current Shield
     Max Shield
     Current Stamina
     Max Stamina
     Current Faith
     Max Faith
     Skill Points

# Ammunition 
     Current Arrow Count

Notes
EDITOR OPTIONS

For Player Stats or Ammunition, enter the game and while you are moving around you will see that the values fill into the editor.  Change them then press TAB to lock the new values in.

Unlimited Items/Ammo/Arrows:
Toggle on and most items when used or consumed or fired do not decrease.