About the computer mouse settings?

Every time I'm on the laptop and open a PDF and scroll down, it jumps back to the top of the page and I don't understand why. Example: scroll to page 5, read something, scroll further and it jumps to the beginning. Can someone please tell me how I change that?

Go to Settings / All Settings, there on Devices / Mouse.

There you can change (try) the settings for the mouse wheel.

If necessary, also install the latest driver software from the mouse manufacturer.