I have had some success by copying and pasting the content out of Word files into the text windows of character cards and handouts. It doesn't do headers, footers, tables, or graphical objects, but it does do fonts, boldface and italic, different point sizes, and paragraph indents and outdents. I think it might be converting to RTF.
I'm looking forward hopefully for PDF support, because print-to-PDF allows me to easily convert anything to PDF. Until (and unless) that happens I'm using screencaps converted to GIF for things that need graphics and table, and RTF for things that need to be edited, and reminding myself that Roll20 is a shared virtual tabletop, not a word processor nor a graphics editing package.