I set up a passcode, what can I do if I forgot it?

If you can’t remember your passcode, you have to connect your iPad to your computer and backup your documents (or only that folder) using the "File Sharing" iTunes feature. Once you have a copy of your documents, you will  need to delete Notes Writer app and re-install it in your iPad from scratch (it’s free).

There is an Apple page about the iTunes File Sharing and how it works:

http://support.apple.com/kb/HT4094?viewlocale=en_US&locale=en_US