NEW YORK — Even as a pared-down version of Microsoft's Office software package arrived on the iPhone, the company is holding out on extending that to the iPad and Android devices as it tries to boost sales of tablet computers running its own Windows system.
Microsoft also isn't selling Office Mobile for iPhone separately. Instead, it comes as part of a $100-a-year Office 365 subscription, which also lets you use Office on up to five Mac and Windows computers. Microsoft made the app available through Apple's app store Friday.
Microsoft Corp. is treading a fine line as it tries to make its subscription more compelling, without removing an advantage that tablet computers running Microsoft's Windows system now have — the ability to run popular Office programs such as Word, Excel and PowerPoint.
Microsoft has been pushing subscriptions as a way to get customers to keep paying for a product that has historically been sold in a single purchase. The company touts such benefits as the ability to run the package on multiple computers and get updates for free on a regular basis.
A subscription can be more expensive than buying the package outright for just one or two computers, but those wanting the iPhone app won't be able to avoid the recurring fees. Microsoft said it wants to give customers yet another reason to embrace subscriptions by offering Office on the iPhone only with a subscription.
The iPhone app will let people read and edit their text documents, spreadsheets and slide presentations at the doctor's office or at a soccer game. But many people will prefer doing those tasks on a tablet's larger screen. Office is available on those devices through a Web browser, but that requires a constant Internet connection, something many tablets don't have.
"The nature of the Office suite, being productivity-focused, makes it better-suited for a larger mobile screen," said Josh Olson, an analyst with Edward Jones. "The issue then becomes, 'How do you provide the Office offering in its best-suited mobile environment without negating a distinguishing characteristic of the Windows 8 tablets?'"
He said Microsoft isn't likely to offer Office on the iPad and other tablets until it sees sufficient adoption of Windows tablets first. Because of that, the new mobile app is likely to increase consumer awareness, but it won't significantly increase subscriptions.