General manager Ray Shero announced the signings Wednesday.
Kujawinski had 21 goals and 15 assists in 34 games with North Bay (OHL) following a trade from Kingston. He had a league-leading two overtime game-winners, while adding three assists in 15 playoff games. The 20-year-old, 2013 third-round draft pick also had 13 goals and 10 assists in 27 games with Kingston this season.
The 22-year-old Pietila had 46 goals and 60 assists in 153 games at Michigan Tech, including career highs of 14 goals and 30 points last season. He was a fifth-round draft pick by New Jersey in 2011.