i fixed the issue returning to mavericks
the issue was only with large pdf files over 400 mb.i had no issue with small pdf files
with mavericks i cannot use iCloud drive and my iPhone cannot connect with retina MBP
i have decreased my storage plan from 200 to 20 gb because i cannot use this extra gb without cloud drive.Dropbox is still working.Thanks god dropbox is not developed from apple
i liked yosemite however i must read my medical pdf files (some pdf files are more than 1,5 gb)
i am going to wait for this issue to be solved and then install yosemite.
With mavericks i never had issue with pdf files even with some pdf files larger than 3 gb(i merged some medical pdf books and created a large pdf file) preview and search are super fast!
i am disappointed nevertheless i hope that apple will address this issue.