Google has a cache, basically, the cache allows you to look at pages as Google crawled them. The question is, at least in a Google Webmaster Help thread, is the Google cache storing everything locally at Google?
John, a top contributor, said that Google stores web pages locally, but all other documents are not stored locally. So that means, if you pull down a web page, but Google cached it, the web page will likely still come up in the cache. However, if Google indexed a PDF or Word doc, and you pulled it down, the cache result will likely not load.
Only if the .doc page was still their server. Google only has a snapshot of the HTML on the particular page, everything else resides on the on the web as is (images, external css, targets of links).
Do note that John is not an official Google representative and I was not able to quickly find supporting documents in Google's help section on this. Of course, you can use the noarchive meta tag to ask Google not to cache your pages, more on that over here.
Forum discussion at Google Webmaster Help.