When you save a document in Pages, Keynote or Numbers '08, there is an option to "Include preview in document." If you tick this box and save, you can view the entire document as a PDF file on any Mac or PC that can open PDFs.
On a PC, the iWork file will show as a folder. Open it and open the QuickLook folder inside of that. Copy the Preview.pdf file to another location, and then you can open it and view it. On a Mac without iWork '08, control-click on the document and select Show Package Contents from the pop-up menu, then open the QuickLook folder and open the Preview PDF.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070824031740561