Hi,
It doesn't work that way. InvisibleElementId and VisibleElementId works on whole element. So for example, if element A contains element B and element A is invisible, then the entire element A is invisible. It is not possible for you to hide only part of element A. In addition, the converter do not recognize @media print either. Our goal is to render everything exactly the same as you see on the screen. So we do always use screen target.
There are a number of options for your case. One way is to add an additional argument to your code (for example, page.aspx?export=1), then modify your code to render output differently. This is very similar to many website that offers a "printer friendly" version for certain pages. Another way is to add additional script in your page to detect whether the page is running inside our converter. If you see the page is running inside our converter, you can do certain things accordingly (for example, to change the CSS class of your body element to turn off background). See here for more information on how to detect the converter with JavaScript:
http://www.essentialobjects.com/doc/4/htmltopdf/eo_js.aspx#checkHope this helps. Please feel free to let us know if you have any more questions.
Thanks!