Pittman is returning to Adams Park after initially leaving the club in 2011, and Ainsworth believes that the forward still has his best years in front of him.
The 40-year-old told Wycombe's official website: "He's a great character but more importantly, he brings a lot to the team and he's still got his best years ahead of him.
"He gives us another attacking option. He's got pace, power and he's exciting to watch, plus he's a fans' favourite."
The former Oxford United player scored 14 goals in 77 league appearances during his previous spell at the club.