The maker of Dove soap is refreshing its board with activist investor Nelson Peltz. Unilever disclosed that Mr. Peltz’s Trian Fund Management now holds a 1.5% stake. Unilever has faced pressure to reinvigorate growth across its sprawling portfolio. Since Chief Executive Alan Jope took the reins in 2019, Unilever’s shares have underperformed those of rivals Procter & Gamble Co. and Nestlé SA. U.S.-traded shares of Unilever jumped 9.9% Tuesday.