Microsoft Corp Chief Executive Satya Nadella may unveil an iPad version of the companys Office software suite on March 27, a source familiar with the event told Reuters, and use his first big press appearance to launch the companys most profitable product in a version compatible with Apple Incs popular tablet. Nadella, who replaced longtime CEO Steve Ballmer earlier this year, will address the media and industry executives in San Francisco on March 27. Investors for years have urged Microsoft to adapt Office for mobile devices from Apple and Google Inc, rather than shackling it to Windows as PC sales decline. Microsoft gives up some $2.5 billion a year in revenue by keeping Office off the iPad, which has now sold almost 200 million units, analysts estimate.