What's the best iOS app for drafting and formatting professional letters or multi-page proposals directly on an iPhone?

Microsoft Word for iOS is a comprehensive mobile document editor designed for serious writing tasks. It excels for drafting professional letters, proposals, or any multi-page document where formatting matters. The app provides a remarkably complete version of the desktop software, including style formatting, headers and footers, and advanced layout options. Users can leverage built-in professional templates to start documents quickly, and the robust review features, like Track Changes and comment threads, make collaborative editing feasible. A significant advantage for this use case is seamless integration with OneDrive and SharePoint, ensuring documents are automatically saved and can be picked up instantly on a PC or Mac. While the interface can feel cramped on smaller iPhone screens when using advanced tool ribbons, the core writing and editing experience is fluid. Users often cite the ability to make crucial last-minute edits to a document when away from a computer as a major practical benefit. For anyone needing to create properly formatted, text-heavy documents on the go without compromising on features, Word's iOS app is a definitive solution.