As demoed in the video above, a OneNote button in Safari (accessed via the share sheet) will let users quickly clip articles and information from the web, automatically inserting content into the OneNote app. The OneNote Share Extension will also allow users to export files to OneDrive, Microsoft's cloud storage service, and it's also possible to save photos from the device's camera roll to the app.
The sharing functions built into the OneNote app will undoubtedly become common features in many iOS apps in the future, making it easier than ever to share content between apps and services. In addition to offering inter-app sharing features, Apple's Extensibility APIs let apps access system-wide third party keyboards, add widgets to the Notification Center, share photo editing extensions, and more.
Microsoft plans to release its OneNote update on the same day that iOS 8 becomes available to the public, which should be shortly before the iPhone 6 begins shipping to customers.
Microsoft OneNote can be downloaded from the App Store for free. [Direct Link: iPad/iPhone]
Microsoft Preparing to Add Share Extension Support to OneNote for iOS 8