But it's not clear that Instapaper is allowed to put the files in Documents. According to the Data Storage Guidelines cited in the article:
1. Only documents and other data that is user-generated, or that cannot otherwise be recreated by your application, should be stored in the <Application_Home>/Documents directory and will be automatically backed up by iCloud.
2. Data that can be downloaded again or regenerated should be stored in the <Application_Home>/Library/Caches directory. Examples of files you should put in the Caches directory include database cache files and downloadable content, such as that used by magazine, newspaper, and map applications.
I don't know if this is something enforced in the approval process, but it seems like Apple's intention is for redownloadable content to all be stored in temporary, wipeable locations.
Still, when user saves a webpage to Instapaper he/she probably wants to see it as it was when it was saved, and not magically updating itself afterwards. So I think that 'exactly this article at exactly this point in time' should qualify as 'content that cannot be recreated'.
1. Only documents and other data that is user-generated, or that cannot otherwise be recreated by your application, should be stored in the <Application_Home>/Documents directory and will be automatically backed up by iCloud.
2. Data that can be downloaded again or regenerated should be stored in the <Application_Home>/Library/Caches directory. Examples of files you should put in the Caches directory include database cache files and downloadable content, such as that used by magazine, newspaper, and map applications.
I don't know if this is something enforced in the approval process, but it seems like Apple's intention is for redownloadable content to all be stored in temporary, wipeable locations.