The popular suite includes Word for documents, as well as programs for spreadsheets and other functions, and the latest version is adapted for devices with touch, stylus and mouse interfaces and links to the cloud to allow access to documents.
Office was designed "from the ground up" to work in harmony with the Windows 8 operating system to be released by Microsoft in October and work intuitively across the range of devices supported by Windows 8, Ballmer said.
"The industry continues to move and change and advance dramatically," Ballmer said.
The new Office comes as Microsoft readies a Surface tablet computer to take on the iPad and seeks to expand in the smartphone market with version of Windows 8 tailored for mobile gadgets.
"Office is a service first," Ballmer. "Office is transforming because of the new systems and operating systems and hardware it can support."
Microsoft corporate vice president Kirk Koenigsbauer used a tablet computer to demonstrate Office features that let people collaborate on projects and share data online in a challenge to the Google Docs software suite.
Skype was integrated into Office to let people launch Internet video calls instantly. The newest version will also link to the online version known as Office 365, which is a cloud-only subscription service.
"Office is designed to be your modern office," Ballmer said. "It incorporates the best of Windows 8, cloud, social, and new scenarios."
The new software was available online at office.com/preview.
The Office suite is considered Microsoft's flagship offering and has long dominated the world of computer "productivity" tools for workers.
However, smartphones and tablet computers have been invading workplaces with employees instead of companies dictating device choices and growing accustomed to using applications and data in "the cloud."
Microsoft built its fortune on packaged software for personal computer users but has been evolving hybrid cloud service offerings to avoid becoming obsolete.
"What is surprising is how they have tied all the things together," IDC analyst Al Hilwa said of Microsoft adapting to the "post-PC era" heralded by the smash success of iPads.
"The smartphone, the cloud, and everything are obviously coming together for them," he continued at the San Francisco event.
Like the Windows 8 operating system, the new version of Office is crafted to work smoothly and intuitively with touch-screen controls that have been hits on tablets and smartphones.
Recent Microsoft acquisitions, including Skype and Yammer, have been integrated into Office to make it easier for people to communicate and collaborate.
While making Office programs more consumer-friendly, Microsoft also played up professional capabilities such as management controls and security that have proven winning features for companies.
"Microsoft has a really strong presence in the enterprise and that is for them to lose," Hilwa said.
"Preserving it will hinge on the level to which they can consumerize, because the enterprise is increasingly subservient to consumers."
Google Docs provides free or low cost programs for text, spreadsheets and other productivity needs as online services.
"Google Docs and Microsoft Office have been in a race for some time," Hilwa said.