Restore ebooks (PDF) from iTunes backup?
There is an application called iPhone Backup Extractor that will help you extract data from an iPhone backup. it will convert the files you see in the backup with randomly generated names to things you will recognise.
When you run the application and identify the backup you want it to use it'll give you a list of all the application data contained within the backup. BTW you'll need to move the backup folder so its sitting at /Users/YOURUSERNAME/Library/Application Support/MobileSync/Backup/LONG_GIBBERISH_STRING for iPhone Backup Extractor to find it.
I'm not 100% certain where Apple stores books/documents that haven't been purchased but my guess would be within either &quot;com.apple.iBooks&quot; or &quot;iOS Files&quot;.