Working Copy support
You might have been in a situation like this before: you have published a document, and you need to update it extensively, but you want the old version to exist on the web site until you have published the new one. You also want the new document to replace the current one, but you'd like to keep the history of the old one, just in case.
Of course, you could make a copy of it, edit the new version, and when the new version is ready, move away the old version, copy in the new version, etc. But there's an easier way to do this in Plone, which is what we call "working copies".
Essentially, you can check out a parallel version of a published document, and Plone will keep track of the two documents together. You can then go off and polish your new document to perfection — and when you're ready for the new version to go live, you just publish it.
Behind the scenes, Plone will replace the old document with the new one in the exact same location and URL — and archive the old version as part of the new document's version history.