Acrobat X Pro - Converting web pages

Question

Windows/IE8
When you use "Convert to PDF" if there is a background border color on some web pages it is not captured.  The page crops to eliminate the border.  The "Use Web page background color" has no effect on this.  The background color is captured, but the border surrounding the main page area is not.
You can capture the entire page using a screen capture tool, but Acrobat doesn't seem to have a way to get this part.  It's a shame because the rest of the convert feature seems to be quite good.
I think what is needed here is an adjustment to set the width of the captured area.  It might even be more than the screen width.
Anyone know if there is any way to do this?

Answer 1

Thank you for that explanation.  I appreciate your response and knowledge.
I assume that is the correct technical answer.  But from my point of view, I don't care so much as to why it doesn't capture it as I do about how can I get it to capture it.  I assume there is no way to do it.
That border part, regardless of what it is technically, is part of what the viewer sees when he views the page.  It seems to me that the idea of the capture feature is to capture the full Web page as faithfully as possible so it looks exactly as it looks when you view the page live and contains all the information contained in the live page.  So, I think it is a flaw in the Acrobat capture feature that this area is not captured.
I use another .pdf program that captures the page including that part of the page.  But I would prefer to use Acrobat if it worked properly.
If there is some good reason why that area should not be captured, I'd be interested in hearing what it is.  It might be something I am not aware of.  If there is some reason, then maybe the best solution would be to offer some kind of option to capture it with or without certain parts such as the part you mentioned.
The other program has a width adjustment so that you can determine how wide tha capture area is.  It's a nice feature and allows you to capture it the way Acrobat does without the border, or make it wider to capture the border too.  Acrobat should have some way to accommodate this.