San Francisco -- Yammer, the San Francisco-based developer of private social networks for businesses designed to help employees more easily collaborate, said it has acquired U.K.-based oneDrum, a developer of file sharing and collaboration software for businesses. Financial terms of the deal were not disclosed. Yammer said the acquisition will allow it to add desktop sync capabilities, enabling file folders to be shared across multiple users' desktops, as well as technology that lets multiple authors work together on Microsoft Word, Excel and PowerPoint documents in real time. "Employees spend a huge amount of time working with files, especially in Microsoft Office," said CEO David Sacks. "Through oneDrum, Yammer will incorporate all of that content into the enterprise social graph, making it discoverable and collaborative." All of oneDrum's employees will join Yammer, with CEO Jasper Westaway leading the integration of the two products. The news comes a month after Yammer raised $85 million in its fifth round of funding, led by DFJ Growth.