Просто используйте doc.output ()
var doc = new jsPDF();
doc.text(20, 20, 'Hello world!');
doc.text(20, 30, 'This is client-side Javascript, pumping out a PDF.');
doc.addPage();
doc.text(20, 20, 'Do you like that?');
// Output as Data URI
doc.output('datauri');
ХРОМ
var doc = new jsPDF();
doc.text(20, 20, 'Hello world!');
doc.text(20, 30, 'This is client-side Javascript, pumping out a PDF.');
doc.addPage();
doc.text(20, 20, 'Do you like that?');
var base64string = doc.output('datauristrlng');
debugBase64( base64string );
function debugBase64(base64URL){
var win = window.open();
win.document.write('<iframe src="' + base64URL + '" frameborder="0" style="border:0; top:0px; left:0px; bottom:0px; right:0px; width:100%; height:100%;" allowfullscreen></iframe>');
}