Hi,

We have PdfExporter class in our Java and .NET libraries, you could use it on server side if running these platforms on the server.

Other than that you could add the diagram as bitmap to a PDF page as shown here -
https://stackoverflow.com/questions/23681325/convert-canvas-to-pdf

I've also played a bit with canvas2pdf library from second SO answer to export as vector graphics (the apply and lineWidth things are to work around some unimplemented method exceptions) -

//Create a new PDF canvas context.
var pdfContext = new canvas2pdf.PdfContext(blobStream());
pdfContext.doc.lineWidth = function () { return 1; }

var canvasContext = diagram.context;
pdfContext.transform = { apply: function() {} };
diagram.context = pdfContext;
diagram.repaint();
diagram.context = canvasContext;

//convert your PDF to a Blob and save to file
ctx.stream.on('finish', function ()
{
	var blob = ctx.stream.toBlob('application/pdf');
	saveAs(blob, 'example.pdf', true);
});
ctx.end(); 

but then it crashes on some code for embedding font files into the PDF, maybe you could get that to run if you set up the font files along with you project.

Regards,
Slavcho
Mindfusion