I've been trying the new pdfviewer from https://tracker.zkoss.org/browse/ZK-439

I modified the project from https://github.com/zkoss-demo/zkpdfviewer-demo to use Media content instead of relative URL in Pdfviewer::src but it does not render the PDF (you can see the change in my forked project https://github.com/aljiru/zkpdfviewer-demo/commit/c710d847b26691eb6ed504fe48e6a318639a33cd).

Finally, after spending some hours debugging I came up with a fix (I share it with you, I don't know if it's the proper solution, but at least it worked for me https://github.com/aljiru/zkpdfviewer-demo/commit/05d742e64ea1e1ed649c1017e96b0efe225240d8)