GoodReader ?
How can I open my pdf books in iBook app by GoodReader App?
I need to see my documents in GoodReader to edit them.
There isn't an easy way to get them there as far as I know. If you have access to your computer then you can copy them over to the Books part of your computer's iTunes library (File > Transfer Purchases, that should copy them even though they aren't iTunes purchases) and save them and use file sharing to copy them to the GoodReader app. If you don't have access to your computer then you can open a PDF in the iBooks app, email it to yourself, and then use 'open in' on that email to open it in GoodReader.