The fourth-seeded American, who claimed his maiden crown in the Swedish capital in 2021, downed the third seed from Bulgaria 6-4, 6-3.
Paul did not drop a set all week and boosted his chances of making the season-ending ATP Finals for the first time.
"I feel like every match I played a little bit better and better," world number 13 Paul said after adding the Stockholm title to triumphs this year at Dallas and Queen's Club.
"Today I came out playing amazing, so I was definitely happy with the performance."