I have reproduced the problem and logged it as PDFNET-5541 in our defect tracking system. We will try our best to fix it ASAP and give you an update then. Thanks.
I tested this issue and found it is not a bug. This problem is related to printer setting. When I print the document with default setting I get the same result as your. But when I set "Page Scaling" to None and uncheck the "Auto-Rotate and Center", the margin in the paper is correct.