To use Dropbox offline I believe that you have to select a file as a favourite on the ipad and this will store it locally? My question is this - once you open a document can you then access that via the iPad whether you select it as a fav or not? I opened a doc and it now opens whether I am offline or online. Is this because it is in some sort of history cache or something. Does it last or do I really need to select it as s fav?