You’ve read all of your free items this month. To register, get added benefits and unlimited access to articles, Become a Member. Already a Member? Sign in. Advertising Age Article Abstract Ad Units in Magazines' iPad Editions Climbed 16% in 2013 But Growth May Have Slowed in the Fourth Quarter By Michael Sebastian, Published on December 30, 2013 0 Want more Access, Content & Connections? Upgrade to Membership. We are glad you are enjoying Advertising Age. To get uninterrupted access and additional benefits, become a member today. Register Now Already a member? Log in.