Outside PDF transfer from iBook to nook

I recently bought a travel guidebook online from an outside source other than iTunes. However, when asked what program I wanted to use to open it I chose iBook. Since the book I downloaded was in PDF format I can not highlight portions of it using iBook. I am wondering if there is anyway to transfer it to nook so that I can highlight passages. Also the device I am using is an iPad if that changes anything. Thanks for any help.