Ackman to Sell Part of His Stake in Canadian Pacific More than a year after the activist investor William A. Ackman won a bitter battle for control of the Canadian Pacific Railway, he is cashing in part of his investment at a substantial profit. On Thursday, Mr. Ackman's hedge fund Pershing Square Capital Management said it would sell around $800 million of its stake in Canadian Pacific, or 5.9 million shares, in an open market transaction at an undisclosed price per share. Following the sale, Pershing Square will hold a 9.8 percent stake in the company and will remain Canadian Pacific's largest shareholder. The move is a victory for Mr. Ackman, who will have nearly tripled his investment in Canadian Pacific, at a time when he needs it most. He first began buying the shares in 2011, when they were trading at about 46 Canadian dollars a share. Shares closed on Thursday at 147.95 Canadian dollars. It's been a difficult year for Mr. Ackman, who has been in the spotlight for bets that have soured. In August, he was forced to retreat from a bruising and public fight at J.C. Penney, and a $1 billion bet that Herbalife is a pyramid scheme has failed to gain traction with shareholders. Mr. Ackman has had more sympathy from shareholders in his campaign against the board at Canadian Pacific, one of Canada's oldest companies. In May 2012, he won a public battle with the board at Canadian Pacific, removing Fred Green, its chairman, and four other board members. He later brought in E. Hunter Harrison, a former chief executive of Canadian National, a rival to Canadian Pacific. The share sale will be led by Credit Suisse, and Bank of America Merrill Lynch and Morgan Stanley will also participate in the transaction.