Changing helper applications triggered by KMail using Gnome DE

[AG <computing.account@googlemail.com>]

Hi list

How does one change or configure the applications triggered by KMail 
within a Gnome DE?

For example, if I click on a KMail link indicating a *.pdf file from the 
web it open Xpdf which, while a fine application in its own right, is 
not what I want triggered - I'd rather use acroread.  Similarly, with a 
URL that ends in *.swf VLC is opened and cannot load the weblink.

I've looked on the web and the suggestions available given my search 
string seem specific for SuSE and suggest that the configuration is done 
via Konqueror.  Under System > Preferences > Preferred Applications 
nothing seems relevant either.

Is there a trick to this or is really a case of configuring this via 
Konqueror because it doesn't seem possible via KMail directly.

TIA for any help.

Cheers

AG