I am new, and my ipad has ios 4. I would like to park some documents on the ipad from my MAC, and be able to read them on the ipad from time to time. Do none of the Apple-supplied apps support file sharing? I am mainly interested in PDFs, but maybe some .txt or .doc files as well. If I have to buy an app for this, how can I select one that works as well as Preview for PDFs, ie supports links, jumping to pages in the index, etc etc?