Please add a Footnote tools. Sometime when taking notes (either by hand writing or keyboard), I want to refer an information from something I wrote to any specific document or any format of information I need to put on which already saved on my ‘IPad books library’ (e.g. .pdf) by adding a footnote. When tapping the footnote, I can browse and choose any doc from my library, open the source, and highlighted the specific information I want to pointed if such reference is an ebook-pdf which contains many pages. Therefore, the exact highlighted information will immediately and automatically show up once I tap the footnote. In addition, if I want to read further information, I can scroll up/down the pdf on the footnote I’ve tapped just like ordinary reading an ebook. The footnote usually set in numbers, please add numbers on tools as footnote numbers. Below, I drop a picture for a sample