A surprise popped up in the iTunes Store Friday: an iPhone version of Microsoft Office.

The app has its limitations. It’s free to download but only works for those who subscribe to Microsoft’s Office 365 service, which costs $10 per month or $100 per year. It isn’t meant for the iPad, whose larger screen would make it easier to work with documents. And it only works with the three core programs of Office: Word, Excel and PowerPoint.

But it is Office. And it’s on the iPhone. That counts for a lot.

Users can edit existing documents started on other screens from Word, Excel and PowerPoint using the app, making it easier to incorporate last-minute changes and suggestions into shared meeting materials that everyone on a team can see.

Users can also make new Word and Excel files from their phones, which is particularly convenient for those times when you want to get a thought or figure down, but don’t have a laptop handy.

Because the app works with Office 365′s cloud capabilities, the changes you make on your phone will show up across all your devices. So the next time you pick up the document on your laptop or desktop, it should reflect all the tweaks you made on the go.

The app comes after long speculation over whether Microsoft would come up with a way to run its essential software suite on smartphones from competitors. Office is one of Microsoft’s most important and iconic products and has been a major selling point for Microsoft’s Windows Phones and tablets running Windows RT and Windows 8.

But adding iOS support gives Microsoft the opportunity to reach a much wider audience in the smartphone market and sell more of the subscriptions it’s pushing for the wider Office suite.

For consumers, it’s certainly a plus. To this point, most of the Office alternatives that have popped up to fill a demand for productivity software on the iPhone are, by and large, not as stable, feature-rich or easy to share with others as Microsoft’s files.

That’s not to say that there isn’t some competition. Google, which has challenged Office with its flexible and portable Google Docs suite, has a Drive app for the phone that also lets users make new word-processing documents or spreadsheets from the iPhone. Users can also upload photos or videos using the app, and edit a wider range of Drive documents.

And Apple announced earlier this week that it’s adapting its iWork suite for iCloud, providing a more competitive product to take on Office 365. The additions mean that Apple’s productivity software will give users a way to work with Pages, Numbers and Keynote files on the Web. Those files will also be Office-compatible, the company said.