I have an HTML report, with each print page contained by a width: 180mm;
height: 250mm
One thing worth revisiting is the validity of your HTML markup if you are using the AddImageUrl method. Instances where the rendered PDF is not as expected can result from bad markup, busted tags, etc.
For what it's worth, WebSuperGoo has excellent support and respond great when you encounter anomalies. Often they can advise a work around or provide alternatives to your implementation if you send them your source code.