I'm not sure that what you want can be done (although other OSes support this functionality), but your post alerted me to the Preview Pane, so thanks for that.
You're very welcome!
You're probably using the default preview handler from adobe. You may want to try the Foxit PDF Preview Handler (Google for it and it's easy to find, get the one for Windows 7). It has extra functions like zoom and text search (as if you're using a full-blown reader). It's free and you can uninstall it anytime.