Canva Inc. acquired the Affinity suite of creative software popular with Mac users, securing its biggest acquisition to date in an effort to compete with Adobe Inc. The deal, which is a mix of cash and stock, is valued at “several hundred million pounds,” Canva co-founder and Chief Operating Officer Cliff Obrecht said in an interview with Bloomberg on Monday. It’s the biggest outlay yet by Australia’s most valuable startup, priced at $26 billion in its latest share sale, and marks a milestone in...