Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
If you get a document with fonts you don't have, the result can be bad. Layout will surely not be proper and for some reason LO and Caligra pick a horrible replacement on my computer - Alien Leage, see screenshot. Guaranteed to make any normal document unreadable. And the idiotic 'reading mode' of LO makes it impossible to change the font until you've saved the file somewhere. The benefit of that mode always escaped me in MS Office, at least I knew how to turn it off...
Anyway, enough ranting - a solution. If you don't have the new Microsoft fonts like the new Win7 fonts including the often-used Calibri, you can start to search the web for obscure download sites where, after you decided not to enjoy some online casino, enlarge a body part or clean your computer from viruses, you might find potential candidates in zip or rar form.