How to make an ajax call to a page and wait for the ajax calls on that page to finish

I am doing a simple ajax call.but in the page i'm calling there's an ajax call to a pdf file. Is there a way to make the page wait until all the ajax calls on the requested page are load? I am getting as well the following error :"Can't create DocumentThreadableLoader"

 $.ajax({
    type: "POST",
    dataType: "text",
    url: '/test/test.pdf',
    success: function (data) {
        $('body').html(data);
    },
    data: body
});