When I attempt a PDF conversion on a PHP page in IE 11 on Windows 8.1 and 7 (only ones tested), I always get an error message: "[name].pdf might have been moved or deleted."
If I click the Retry then the file finishes downloading. You may view this behavior at www.saladbars.com by clicking on the Print to PDF button at the top of the site.
I have PDFNetSDK 5.8 with the HTML conversion add on.