Create PDF file from iframe

I want to save a PDF file which contains an IFrame content. I am using jsPDF for it. When I hit the button that calls the function the script creates an empty PDF page.

The content of the frame looks like: https://jsfiddle.net/ss6780qn/

I am using the following script:

<script src="../jspdf/plugins/standard_fonts_metrics.js"></script>
<script type="text/javascript">
function toPDF(){       
        var pdf = new jsPDF('p', 'in', 'letter');

    // source can be HTML-formatted string, or a reference
    // to an actual DOM element from which the text will be scraped.
    source = $('#frame')[0]

    // we support special element handlers. Register them with jQuery-style 
    // ID selector for either ID or node name. ("#iAmID", "div", "span" etc.)
    // There is no support for any other type of selectors 
    // (class, of compound) at this time.
    specialElementHandlers = {
        // element with id of "bypass" - jQuery style selector
        'div': function(element, renderer){
            // true = "handled elsewhere, bypass text extraction"
            return true
        }
    }

    // all coords and widths are in jsPDF instance's declared units
    // 'inches' in this case
    pdf.fromHTML(
        source // HTML string or DOM elem ref.
        , 0.5 // x coord
        , 0.5 // y coord
        , {
            'width':7.5 // max width of content on PDF
             ,'elementHandlers': specialElementHandlers
        }
    )

    pdf.save('Test.pdf');
}

Does someone know what is wrong and how I can fix this?