Wanted: PDF Highlighter

I need a feature implemented, and I doubt I can just email adobe to have it done.
I need a way to high-light and make notes in PDF documents, without destroying the original.
Alternatively, you could turn highlights off and on, and they would still be contained in the document, but you could still choose to render it in its default format. This, however, would create problems with signing of documents, so I think a file accompanying the PDF would probably be the best.
When I'm reading something that I find interesting, I'd like to mark it for future reference, just like I'm able to scribble in the margins of a piece of paper. I want this functionality available in PDFs as well. It's certainly not hard to implement, but getting Adobe to do it might be a bit trickier.
Preferably, if the scribbles in the margin could take shape as either text, or some referenced things (like adding comments in a Microsoft Word Document), it would be good. (Text takes up a lot of space, and I might want to write a lot in the margin. This is where PDF could actually surpass paper). Of course, having the option of printing the PDF either with the mark-up or without would also be great.

So please, if anyone from Adobe reads this, or anyone with any kind of influence, please tell them about this. I've been dying for something like this since forever (come to think of it, I might have actually blogged about it before)

Likewise, if anybody knows about any plug-in for Acrobat Reader that will let me do this, I'm all ears.

I wonder if there's a suggestions@adobe.com or something. I'm going to check it out. They might have already thought about this, but decided for unknown reasons to not implement it.

EDITED TO ADD: Silly me, Acrobat Reader already has these tools, but you need to use PDFs with "document rights" enabled. To this day I have never come across a document like that. I wonder if there's a hack to let me change that by my self. Stay tuned...