The Smooth Page Scroll Up/Down Buttons plugin for WordPress adds buttons to every page of your site, that can be used to (smoothly) scroll up or down exactly one screen/page at a time. This can be particularly handy for pages with a lot of text/content, or in cases wherever a browser’s scrollbar is just not good enough (or not present at all, like on tablets) to enable one-click, one-screen scrolling.
BONUS BUTTON! Optionally, you can add a “Back to top” button, that will take the visitor right back to the very top of the page.
No knowledge of any coding (HTML, CSS, JavaScript, PHP) is required at all.