I've search online and can't find a good answer to this. I am trying to annotate notes in Apple Books with the Apple Pencil on an iPad Pro 10.5. From what I read you want to convert the book to a PDF in Apple Books which then allows annotations, but when I click the book options and select "Add to Collection" the PDFs option is grayed out. I am on iOS 12 Any help would be much appreciated. Thank you.