[Swftools-common] How to get ri of the marked area (overlay) of a link when hovering over?

[Hans J Nuecke]

I'm looking for a way to get rid of the "grey box" that pops up when 
hovering over a link.
This box/feature is included by pdf2swf. The link in the original PDF 
file is set to "hidden rectangle" without any markups or color.
Viewing the original PDF In Acrobat reader, only the cursor changes, but 
no "grey box" appears.

How to get rid of that overlay/mark up effect?
Can it be influenced by any switch?
Has the final swf file to be manipulated (how?)?
Or is a software modification necessary?

Thanks
Hans