Hi and welcome. At the moment all I can think of is Evernote recently updated with handwriting recognition, if you use that. Microsoft's Office Mobile also very recently released a free version for Android of word, excel and powerpoint, and a separate app for One Note. You could use it on the S4 but it's more useful on the bigger screen (not that the S4 is small!).
If and when you get to know S-Note, there is a better version that comes with the KitKat update, version 3.1.0, which you may already have.
There are 3rd party S-Pen apps in the Play Store and in Samsung apps.
There is also a thread currently running on what everyone favourite apps are.
http://forums.androidcentral.com/sa...-whats-your-top-android-apps.html#post3534541
Feel free to ask in any thread, or start a question.