A few days ago, I was using a desktop at home to try to print a .docx document (from Word 2008). Unfortunately, the home machine had a much older version of Office, and it couldn't open the .docx format.
As a workaround, I uploaded the .docx document into Google Docs, edited it a little bit, and then clicked Print. This converts the document into a PDF, so all you need to do is save that window to create a local PDF. (This also works if you create a document using Google Docs and click Print.)
[robg adds: Another way to do this would be to send the .docx file through Microsoft's Open XML File Format Converter. After conversion, you could then open the document in older versions of Office.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100313205859929