I searched and didn't find anything concerning this issue. This morning, I go to open a textbook(pdf) and some other pdf files in my documents to find them missing, gone, presumed deleted. You can imagine that I was PO beyond reason but swiping down on preview (3 finger swipe) revealed that the files still existed elsewhere. So after searching, I found that the files had copies stored in iBooks directories but the original files that were in my documents were no where to be found. I was wondering if this was a "feature" of iBooks or a bug. I know iBooks imports pdf's but deleting the original file is something I think is out of the norm. Anybody else experience this? As you can see from the image, it looks like files were deleted at random or went missing. I do not use iBooks to open the pdfs, (because they simply open in preview regardless), but just open the pdfs themselves from my documents folder.