According to the ACG Swashbucklers:
"At 3rd level, while she has at least 1 panache point, a swashbuckler gains the ability to strike precisely with a light or one-handed piercing melee weapon (though not natural weapon attacks), adding +4 damage dealt. To use this deed, a swashbuckler cannot attack with a weapon in her other hand or use a shield other than a buckler. She can even use this ability with thrown light or one-handed piercing melee weapons, so long as the target is within 30 feet of her".
I have a Swashbuckler 4 (attached).
I went to Temp Bonuses and added "Swashbuckler Initiative" and "Precise Strike (Rapier)".
On the built-in character sheet, and in the PDF export, no extra damage is applied
(though the Temp Bonus system is system is working overall, as Initiative gets the has-panache bonus +2).
pathfinder core supplements ruleset
I can't yet tell if Temp. Bonus will correctly stack Precise Strike and Power Attack. As soon as Precise Strike works, I'll be checking the combination (which is the intended melee pattern for this fellow!)