When it comes to working with office productivity apps on a Mac (word processing, presentations, spreadsheets, etc), there are lots of options these days. OpenOffice, Google Docs, Microsoft Office and Apple iWork are four of the more common solutions, each with their own set of strengths and weaknesses. My personal preference is to use Apple's iWork suite. Primarily, because it integrates so well with everything else I do on my Mac, and secondarily, because the UI (User Interface) is much easier to use (they remove the unwanted clutter, and give you the things you actually use) than the alternatives.
Here's another feature I really love about iWork... the ability to roll back to previous versions of a document (called "versioning"). Each time you save your document, it saves a snapshot of that version of the document, and stores it as part of the document.
To roll back to a previous version, click on the down arrow next to the name at the top of the window, and choose "Browse all versions..." Doing this will engage a Time Machine-like feature that will show you all available versions of that document. At this point, all you need to do is browse until you find the version you want, highlight it, and click "Restore". It's that simple.