The heart of Pinchboard is iCloud. Without it Pinchboard will not able to save your documents. You may ask "why iCloud need to turn on?". Think about this.. You upgrade to new iPhone. Your document on your previous iPhone will appear automatically on your new iPhone. Just redownload the App and iCloud will handle the rest for you.
Then the next question you might ask is "do I need internet connection to run this App?". One of the problem of App that use Cloud Storage is you need to have internet connection to save the file. Imagine you are in the train and you are drawing something on your iPhone, then the train enter into tunnel. You will receive error message e.g. no internet connection. No worries, Pinchboard will work with or without internet connection. If you had limited data plan, make sure you disable use cellular data for iCloud Documents.
Assuming you disable use cellular data for iCloud Documents. Just like the new feature on iOS 7 that update App automatically in background. When your iPhone, iPad or iPod Touch connected to Wi-Fi, your document will update automatically to iCloud, and if there's new document in iCloud, it will download for you automatically.
For more information on iCloud, go to www.apple.com/icloud