Per NHL radio's Josh Rimer:
A nice depth pickup, if nothing else. Williams, who's been around since he broke in with Detroit in 2000-01, has been a pretty productive player at times. His last healthy season, in 2009-10, he scored 19 goals and 18 assists, splitting duty with the Atlanta Thrashers (RIP) and the Columbus Blue Jackets. In fact, Williams put up 29 points (12 goals, 17 assists) in just 39 games with Columbus.
Injuries have taken a huge toll on the soon-to-be 31 year old. He was on a two-way deal with Dallas last season and only appeared in 27 NHL games (and 17 AHL games). He's had issues from a broken fibula to a hernia to concussions in the past.
Williams has been most successful with the Red Wings, where he's played 277 games in two separate stretches. Williams also has won the Stanley Cup with Detroit, way back in 2002 (though obviously he didn't have a huge role on that star-studded team).
And with all the signings, a look at a quick and dirty depth chart to give an idea of how the Pens look at this point.
Centers- Sidney Crosby, Evgeni Malkin, Jordan Staal, Mark Letestu
Top six wingers- Chris Kunitz, James Neal, Tyler Kennedy, Steve Sullivan
Bottom six wingers- Pascal Dupuis, Matt Cooke, Craig Adams, Arron Asham
13th forward- Steve MacIntyre