"Invitations sent using this feature contain a special key on the document link. This feature can be disabled at any time to expire previously distributed invitations which contain that special key. To do this, simply disable this feature by unchecking it -- in documents and presentations, it's called 'invitations may be used by anyone' and in spreadsheets it's 'editors can share this item,'" Rochelle wrote.

Privacy and security controls in Google's hosted applications have been in the news recently. Last week, the Electronic Privacy Information Center filed a complaint asking the U.S. Federal Trade Commission to stop Google from offering hosted services that collect data until privacy controls can be verified.

Earlier this month, Google acknowledged that a glitch in Docs caused some documents to be exposed to users without proper permission. The problem occurred among users who had previously shared documents. The company said it affected fewer than 0.5 percent of documents.