Copy PDF file to iBooks library

I'm developing a sample app that user can read pdf file, pdf files in my app bundle and i use web view to read these files. Now i want to add a button that allow user click to and copy pdf file to iBooks library, that means when user perform this action, after that, when user opens iBooks app, this PDF file is already available in library of iBooks. Any idea for this problem, plz helps me, thanks alot. PS: i want to make as this link, but i dont want open pdf file immediately in iBooks when user click button, i just want when user open ibooks after that anytime, user can see this pdf book in book shelf