//Use manual trigger mode
HtmlToPdfOptions options = new HtmlToPdfOptions();
options.TriggerMode = HtmlToPdfTriggerMode.Manual;

//Use a HtmlToPdfSession object to gain access to the underlying WebView object
using (HtmlToPdfSession session = HtmlToPdfSession.Create(options))
{
    session.RunWebViewCallback(() =>
    {
        //Load the Url you wish to convert
        EO.WebBrowser.NavigationTask task = session.WebView.LoadUrl(url);

        //Wait for the main page to finish loading --- note that this 
        //does NOT mean all the dependency resources such as the
        //image in question in your case has finished loading. It only 
        //means the main page has finished loading
        task.WaitOne();

        //Use a timer to trigger the conversion. You must use setTimeout to
        //to set the trigger because RenderAsPDF reset the trigger
        session.WebView.EvalScript("setTimeout(function(){eopdf.convert();}, 2000);");
    });

    //Wait until eopdf.convert() to be called and then start conversion
    session.RenderAsPDF(Pdf_file);
}