I work in Marketing and specifically need to use Microsoft Publisher. My pc was just equipped with Libre Office 4.2. If I download Microsoft Publisher will it work with Libre Office, without any other Microsoft products on m my pc?
Upgrade to 4.3.4 that was released recently, assuming Window$: http://donate.libreoffice.org/home/dl/win-x86/4.3.4/en-US/LibreOffice_4.3.4_Win_x86.msi
You find a comparison on features and supported file formats here:
https://wiki.documentfoundation.org/Feature_Comparison:LibreOffice-_Microsoft_Office
A test might also be a good idea.