Penner received his law degree from Hofstra University in Long Island, New York after receiving a secondary education at Selwyn House School and earning an undergraduate degree at McGill University, Montreal, Quebec. He began his career as a lawyer in New York, first with Rivkin Radler & Kremer then with the Olsten Corporation.
Penner joined PEDS in 1998 and acquired the company in 2006. He managed the company through the economic downturn that began in 2008 when many manufacturers began exporting production overseas and returned the company to profitability. Penner became an advocate of the Made in the USA program, which aimed to bring back manufacturing to the United States. The company expanded into the United States in 2011 through the acquisition of the assets of International Legwear Group (ILG), which included the brands PEDS and MediPEDS. On March 11, 2015, PEDS opened a state-of-the-art manufacturing plant in Hildebran, North Carolina with Governor Pat McCrory in attendance.
U.S. President Barack Obama invited Penner to talk about PEDS' investment at a roundtable discussion at the White House in 2014.
In 2016, Gildan Activewear Inc. purchased PEDS for US$55 million.
On October 8, 2014, Quebec Premier Philippe Couillard announced that Penner would replace Pierre Karl Péladeau as Chairman of Hydro-Québec. He is the first anglophone and youngest person to hold this position. He confirmed that Hydro-Québec would not be privatized.