It looks like there are ways to do it, but the file gets converted to an iWork document which may not be what you want.

https://discussions.apple.com/thread/3379754?start=45&tstart=0

If you only need to read the file, not edit it, I'd suggest printing it as a PDF and saving that to icloud.

Marcus L. Rowland
Forgotten Futures, The Scientific Romance Role Playing Game