Adding an index tabs option for samsung notes

I've been using my samsung tablet for a year now, and i haven't downloaded any software where i can put my notes in. I've just been using the samsung notes app, creating folders, and compiling my things there, as well as writing notes. However, whenever i uploaded book pdf's to study, i find it very difficult to scroll up and down and wonder where that page from the previous chapter is. 

I think index tabs would be very helpful, like the tabs we stick on the side of our book to mark a chapter, or to mark an important part of the book. If such an update would be developed, i think it would help a lot. Bookmarks is not just doing it for the notes anymore. I want to see it digitally on the side of the pdf's or such indication on the side of the screen where i can click and go to that specific part of the pdf.