internal link: "open in new tab"-option
Clicking on internal links in pdfs make you jump to the pointed position: E.g. in scientific papers, if you click on the source number you jump the source which is normally at the end of the pdf.
If you want to continue reading it is (as far as I know) impossible to jump back. It would be nice to include some options inspired by browsers: I would like to have the option to open the same pdf in a new tab/window again at the desired position so that after checking the source you can continue reading in the original tab. Also buttons to jump back/foward would solve this problem.