Documents Free is a basic Office suite for iOS.
The package offers a spreadsheet and a simple text editor. Exactly how simple is indicated on the official feature list, which talks of "full support for .txt and .csv files" but only "limited support for .doc, .docx, .xls, .xlsx".
This isn't a package you'll use interchangeably with a desktop office suite, then, but it's fine for doing basic work from scratch. The text editor works for rich text notes, the spreadsheet supports formulas, formatting, resizing and more, there's a file browser to help you view iPhone files, and handy integration with Dropbox and Google Sync.
It's not a "real" Office suite, but Documents Free is fine for basic office work, and you can't beat the price.