JSFiddle - React, Tailwind, and code Playground

HTML

<div class="Choix">
<input type="radio" value="15" name="ChoixExportationPDF" onselect="enabled"  />
                    les <select id="NombrePagePDF">
                    <option value="5">5</option>
                    <option value="10">10</option>
                    <option value="15">15</option>
                    <option value="20">20</option>
 
                </select> premières pages </div>

JavaScript

var listRadio = document.querySelectorAll('input[name=ChoixExportationPDF]');

var selectList = document.getElementById('NombrePagePDF');
selectList.onchange = function(){checkRadioByValue(this.value)};
function checkRadioByValue(value){
    var i,currentRadio;
    for(i=0;i < listRadio.length;i++){
        currentRadio = listRadio[i];
        if(currentRadio.value === value){
            currentRadio.checked = true;
        }
    }
}