Weapon Specialization Pathfinder 2e. Knife: The target takes 1d6 persistent bleed damage 283 2.0 Choose one creature adjacent to the initial target and within reach.

Most martials get critical specialization automatically by a certain level You can get it via ancestry feats for specific weapons Knife: The target takes 1d6 persistent bleed damage

The rogue's level 15 class feature specifies: Your damage from weapon specialization increases to 4 with weapons and unarmed attacks in which you're an expert, 6 if you're a master, and 8 if you're Combat Trick (from the Combat Stamina feat) Source Pathfinder Unchained pg That would mean the Weapon Specialization Rogues get would be different from the Weapon Specialization Fighters get

. Knife: The target takes 1d6 persistent bleed damage Fighter gets it automatically for their chosen weapon group by level 5

. Pick: The weapon viciously pierces the target, who takes 2 additional damage per weapon damage die Mythic Weapon Specialization Source Mythic Adventures pg