I downloaded the xkb definition file:
copied it as /usr/share/X11/xkb/symbols/ur
made an entry in /usr/share/X11/xkb/rules/base.lst
Find the lines as:
en_US U.S. Engilsh
. . .
then in terminal (or konsole) entered:
xkbcomp -lhlpR '*' -o ../symbols.dir
(don't ask me what it means, I don't know!)
Finally in KDE Comtrol Center, enabled Keyboard Layouts, and selected the newly entered entry for Urdu.
and that's it !