The question doesn't make a lot of sense in the software world either...
nonetheless, to do this in Wavelab
1. Open the mono file in Wavelab
2. Edit | Select | All
3. File | Save Special (Wave) | Convert
4. Check the radio button for Stereo, and set the desired bit depth and sample rate, and click OK
5. Give the new file a name and click save.
Obviously this will simply give you a stereo file with a duplicate left and right track, since the starting material is a monophonic source.