Use Numped + to skip forward, Numepad - to rewind and Numpad Enter to play/pause

Control buttons for naturalreaders.com.user.js

// ==UserScript==
// @name         Control buttons for naturalreaders.com
// @author       CanYouJustWorkPlease
// @version      0.1
// @description  try to take over the world!
// @match        *://*.naturalreaders.com/*
// @grant        none
// @require      http://code.jquery.com/jquery-3.3.1.min.js

// ==/UserScript==

// Use Numped + to skip forward, Numepad - to rewind and Numpad Enter to play/pause 

var $ = window.jQuery;
$.noConflict();

var script = document.createElement("script");
script.setAttribute("type", "application/javascript");

script.textContent = "(" + function(){

    // Play on Numpad -
    $(document).keypress(function(e) {
        if(e.code == "NumpadSubtract") {
            $('#playBtn').trigger("click");
        }
    });

    // Forward on Numpad +
    $(document).keypress(function(e) {
        if(e.code == "NumpadAdd") {
            $('#forwardBtn').trigger("click");
        }
    });

    // Rewind on Numpad Enter
    $(document).keypress(function(e) {
        if(e.code == "NumpadEnter") {
            $('#rewindBtn').trigger("click");
            e.preventDefault();
        }
    });
} + ")()";

document.body.appendChild(script);