Hi gayatri,
If you are using Region mode then if there is a direct way to scroll then that would be beneficial.
What I mean is for example you are on Page 1 of a Pdf. If you spy the textbox at the top where you enter the page number using Region mode, then you can enter "2" inside it and then hit enter so that it goes to the next page. This is just an example to give you an idea. You need to identify something of that sort in your application.
But if you are looking for Sendkeys then below are the options-
PAGE DOWN {PGDN}
PAGE UP {PGUP}
UP ARROW {UP}
DOWN ARROW {DOWN}