In 2004 the Inquisitor rulebook was made available as a free PDF within the specialist games section of the Games Workshop website. It’s reposted here for ease of access.
Downloads
Part 1: The rules for playing the game – actions, movement, shooting, close combat, injuries, awareness, special abilities and the armoury.
Part 2: Character creation guides, sample characters, gamesmastering guide, sample scenarios and additional rules on encumbrance, lucky shots and knockback.