If you'd like to keep some of your files from prying eyes, Password Pad lets you create text documents and protect them with either XOR encryption or Triple DES encryption and share them via e-mail, iCloud, Dropbox, or iTunes file sharing.
There are free and paid versions of Password Pad in the Mac App Store. Password Pad Lite is free and supports XOR encryption, which the app itself admits "might be easily cracked." The $4.99 Password Pad app supplies stronger Triple DES encryption. I tried out the Lite version because all I am trying to do is keep Christmas lists and the like from my curious or nefarious children. There is but one iOS version of the app; it costs $1.99 and uses Triple DES encryption.
On a Mac, Password Pad Lite looks like a simple text editor. When you create a new file, you'll be asked to give it a password.
On iOS devices, Password Pad is a universal app designed for both iPhone and iPad, but it works better on the iPad. On the iPhone, the app does not rotate into landscape mode, which provides a wider keyboard for faster text entry.
Tap the "+" button in the upper-right corner to create a new document. You must first save a document to your device before you can move it to iCloud or copy it to Dropbox. You will need to sign into Dropbox first by tapping on the Dropbox button at the top of the display. Once you authorize the app, the Copy to Dropbox button gets added to the lower-right corner.
The iPad and iPhone apps do not sync with one another, but the iOS app makes it easy to share files via iCloud and Dropbox. When viewing the Local Device Files list, tap the Move to iCloud or Copy to Dropbox button and then tap on a file to move or copy. While you can open files you have stored in iCloud or Dropbox to view and edit them, I did not find a way to save a local copy of a file stored in iCloud or Dropbox to my iPhone or iPad.
The iOS app is about as basic a text editor as you'll find. The Options button lets you discard changes, change the password, or show the find bar. The find bar presumably lets you perform a text search, but it did not work in either my iPhone 4S or iPad 2. The find feature, however, did work on the Mac app. The Mac app also provides some formatting options, including font type, size, and color.