Hi,
There is no easy way to do this because a HTML file will always have a solid background (by default it's white). So in order to fill the background with a solid non white color, you will need to:
1. Use HtmlToPdf.Options.BeforeRenderPage to set a before render page handler. This handler is called before the HTML to PDF converter generates output on a page. The event arguments will give you the PdfPage object. At this stage the PdfPage object is blank. You can fill it with a solid color using ACM interface. See here for more information on how to use ACM interface:
http://www.essentialobjects.com/doc/4/acm/overview.aspxDuring this stage you will fill the entire page area, including the page margin area.
2. Once you fill the page with a solid color (for example, blue), then the converter will proceed to output on that page. During this stage the main output area (excluding margin, header and footer) will have your HTML page's background color (by default white). Thus after this stage the main output area will become white. In order for you HTML output area's background color to match the whole page's background color, you must apply the corresponding CSS styles on your HTML. For example, if you want HTML area to be blue, then you can apply body { background-color: blue; } in your CSS.
Hope this makes sense to you. Please feel free to let us know if you still have any more questions.
Thanks!