Papillon was born in Rimouski, Quebec, and grew up in Quebec City. She earned a BA in public communications, law, and history[3] and pursued advanced studies in journalism at Université Laval.[4] She specialized in international politics and field journalism while studying at the Université catholique de Louvain in Belgium, and performed an internship at Radio-Télévision belge de la Communauté francophone.[4] Back in Quebec, she volunteered for humanitarian organizations.[4] At the time of her election, she worked for the Institut de la statistique du Québec.[3][4]
Running in her first campaign, she defeated incumbent Bloc Québécois MP Christiane Gagnon[5] with a margin of 7,709 votes in the 2011 Canadian federal election. Owing largely to its unprecedented success in Quebec, where it won fifty-nine out of seventy-five seats, the NDP won Official Opposition status at the federal level for the first time in its history. Papillon was one of fifty-eight Quebec New Democrats elected for the first time in 2011.