The best method to ensure inter-operability between both systems is as follows
1.For reading ,editing kannada(or any other) documents created on Microsoft Word with Nudi
on Libreoffice Writer
It is possible to read documents created with Nudi in MS Word on LibreOffice Writer by installing(copying) the Nudi fonts(available with Nudi5 installer zip) in /usr/share/fonts
(with root permission and read acess to users) and do
LibreOffice application will have Nudi fonts in it.
However it is not possible to edit Nudi fonts on LibreOffice installed on Ubuntu
only Lohit kedage fonts will appear
Therfore to both read and edit under one hood the best solution is to install latest Wine program
and on that install LibreOffice.exe Windows executable also install Nudi 5.exe program on Wine
use scroll lock to write Nudi text in LibreOffice.This way all fonts work for both read and edit
2. To read, edit Kannada documents created on Libreoffice with Unicode fonts (kedage lohit etc) on Microsoft word in Windows.Install all unicode fonts on Windows.