IPhone : How to get NSData from pages-File in Xcode?

I'm trying to get the NSData from a .pages-file which got downloaded by the UIDocumentPicker, but when I use

NSData *data = [NSData dataWithContentsOfURL:url options:0 error:&error];

or

NSData *data = [NSData dataWithContentsOfFile:url.path];

I'm getting an error that the url points to a directory.

I've already tried the solution from this post, but it didn't work for me.

How do I get the NSData from this file?