Langmack played 174 first-grade games in eight Canterbury seasons, winning titles in 1984, 1985 and 1988.
He died on Thursday morning aged 61, reportedly from a massive heart attack.
His final premiership came under Phil Gould, who said: "I am devastated to learn of Paul's sudden passing this morning."
Langmack represented Australia in 10 Tour matches, NSW in four State of Origin games and NSW City.
He was Rugby League Week Player of the Year in 1992 and Dally M captain of the year in 1995.
After leaving Canterbury at the end of 1990, he played for Western Suburbs and Sydney City Roosters, retiring in 1999.
He later assisted Wests Tigers and coached South Sydney in 2003 and 2004.
Gould said Langmack volunteered for Bulldogs community initiatives and established mental health programs for young people and current and former players.
Gould called him "A true Bulldog."