iBooks pdf's untitled how can I assign a tithe?

[boriken55]

I have a lot of PDF eBooks and documents in iBook, however some of them when downloaded are not showing the title and appears only as "untitled". The problem is that I have too many and it is a waste of energy and time.
Does any one know how can I title or retitled those books and documents.:ipad-keyboard:

Thank you

Boriken55
Ipad2, 32,WiFi