For those iPhone users who are NOT devoted to only ever using free apps, here are two useful business apps I use and recommend. They are NOT free, but they are very good value for (very little) money.
This app (under $15) extends the functionality of Microsoft Office, allowing the creation and edit of Word, Excel and PowerPoint files. The separate desktop application for your PC or Mac handles synchronization of documents between phone and computer. The user interface is cunningly designed to minimize the disadvantages of the small display area.
This has quickly become my best productivity app. Search for this in the App store.
For $5 (or technically, just under), add professional signatures to your outbound emails from you iPhone. This app fills a need for just about any business person using an iPhone to send email. Multiple signatures, with logos, photos, social media links, and more - in fact your iPhone signature will probably be an improvement on your existing desktop version.
Search in app store or visit http://www.ideasunplugged.com/signature.
What business apps are other iPhone users very pleased with, and willing to recommend?