In an important step towards making its note-taking and notebook-authoring service available in more places, Microsoft today has released a pocket-sized version of its OneNote application for Apple's iOS.

The software lets users make things like bulleted lists and checklists, as well as grab and insert photos from the user's photo library or the camera app. All these things can be combined into one note with a slightly modified version of the iOS keyboard that adds feature shortcuts just above the keys.

OneNote on the iPhone (click to enlarge)

OneNote Mobile for iOS shares a similar feature set to its cousin on Windows Phone 7, both in its authoring tools, as well as the capability to sync up to Windows Live SkyDrive. This means users can pen notes within the app, sync up, then continue working on them through the OneNote software back on their PC--and vice versa.

In a call with CNET about the app earlier this morning, Jason Bunge, who is the senior director for Office Product Management at Microsoft, said SkyDrive sync works just like it does on Windows Phone 7, but that everything else about the app has been made to fit in and feel like a standard iPhone app.

"We certainly optimized each app for the device that it runs on," Bunge said. "So if you go and download OneNote for the iPhone today, it will feel like an iPhone app, just as if you look at Office Mobile on the Windows Phone and the OneNote experience on that device, it absolutely feels integrated with that Windows Experience."

OneNote currently has some 80 million users in the U.S., all of which are coming from the company's Office software on the PC. And as for why it's arriving on iOS before the more well-known Office applications like Word, PowerPoint, or Excel, Bunge said it's a better fit for the needs of the mobile office worker.

"We absolutely want to make sure we're delivering the right mobile experiences to our broad Office customer base, and note-taking absolutely popped to the top," Bunge said. "We also know from Windows Phone 7 use, that note-taking ability in that app is one of the most-used Office features, so for us this was a natural priority, frankly, to address user needs and feedback," he said.

Microsoft plans to charge for the application, but as part of a limited time offer is making it available as a free download. How much it will cost, and when the free offer runs out, the company has not yet said.

OneNote joins a select handful of other iOS apps made by Microsoft, like Bing, Wonderwall, Windows Live Messenger, Tag Reader, and the now-retired Sea Dragon app, which was the company's first iPhone effort. When OneNote's price does--eventually--go up, it will be the first paid application in Microsoft's portfolio.

Update at 10:32 a.m. PT: We've just heard the application is currently available only for U.S. App Store users. No word yet on if, or when it will be available in other markets.