Starfield Skills -> Combat Skills
Pistol Certification is a skill in Starfield located in the Combat skill tree that improves player damage and critical chance with Pistols.
Pistol Certification Skill Description
Considering the popularity of the personal sidearm in the Settled Systems, familiarity with such weapons is often considered essential.

Pistol Certification Skill Ranks
Rank 1
Pistols do 10% more damage.
Rank 2
Pistols do 25% more damage.
Rank 3
Pistols do 50% more damage.
Rank 4
Pistol kills grant +25% critical hit chance for 5 seconds.