The 36-year-old Sydor played with Dallas from 1995-2003, winning the Stanley Cup with the Stars during the 1998-99 season and appearing in the finals again the following season.
He was dealt to Columbus in July 2003 before being traded to Tampa Bay in January 2004, where he helped the Lightning win the Stanley Cup that season.
The 35-year-old Boucher has three assists and 15 penalty minutes in 16 games this season. A former All-Star defenseman, Boucher is six points short of 300 in his career.
Sydor was held out of nine of the Penguins' 17 games this season, getting one goal and one assist in eight games. Last season, he was scratched for nearly two months before playing the final four games of the Stanley Cup finals against Detroit.
"I didn't wanted to go out the way so many old guys have, not that I consider myself an old guy -- I'm only 36," Sydor said. "It was a matter of numbers here. It was a matter of young guys playing well. I wanted to extend my career, and that wasn't going to happen here."
Sydor signed with Pittsburgh before the 2007-08 season. He had one goal and 12 assists in 74 regular-season games, only to be benched for the first three rounds of the playoffs.
"I was never really told why I wasn't playing," Sydor said. "I proved to myself that I could still play [against Detroit]. It was pretty gratifying to know that after missing 60-some days, I could step in against a great team and still have success."
Boucher, who played for the Kings from 1994-2002 before joining the Stars, has 20 or more points in five of the past six seasons.
Both players count about $2.5 million toward the salary cap and are eligible for free agency next summer.