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.