Hi Thomas,
I regret for the long delay in getting back with you.
I am afraid that I was not able to reproduce the issue. I have created a simple sample to test this issue and it is available in the following link.
http://files.syncfusion.com/samples/pdf.windows/Sample_F78945.zipPlease have a look at the above sample and if still the issue exists, could you please try reproducing it in the above sample or send us the HTML file so that we could sort out the cause of the issue and provide you a solution?
Regards,
Suba