Northwestern Mutual Wednesday announced it will acquire LearnVest, an online advice platform that also provides one-on-one financial counseling through financial advisers. As part of the deal, Northwestern Mutual will be bringing on 1.5 million LearnVest users, plus 25,000 clients through LearnVest at Work, a year-old program where the company works directly with employers to provide financial planning services to employees. LearnVest also has 10,000 premium clients, and a total of 150 employees working out of New York and Arizona.