For example, the pdf file could be a research paper or a book and it has a complicated diagram on page 10, and text in page 11, 12, 13 refers to this diagram constantly. Or page 100 has a complicated example and text in page 200 refers to the example in page 100. The example or the diagram is complicated in the sense that I cannot recall its details easily without looking at it. If I were reading this pdf on a desktop computer with a large monitor, I would open two windows side by side, one window displaying page 100, another window displaying page 200, and if the monitor was small, I would have two maximized windows and I would be Alt+Tab-ing between the two.
If I were reading this pdf on my Android smartphone while I was on a bus, what can I do to easily switch between viewing of page 100 and page 200?
A workaround I use for now is to take a snapshot image of page 100, and then switch between an image viewer (for viewing page 100) and pdf reader (for viewing page 200), and I wonder if there are better ways.