Archiving obsolete materials created in Drupal

What is the best way to archive documents created and used in a Drupal intranet? I work for an NGO that is setting up their intranet using the drupal platform, and we are organizing our materials using "documents" under each "group". These documents are office policies, forms, etc. They are updated every year or so. We would like our employees to have access to the old versions while being able to identify the most current iterations of these documents. So far we are considering having all the documents uploaded to one "document" and then un-linking the obsolete files so that they do not appear to the user unless the user looks for them by "editing" the document. Not sure about the long-term usefulness of this, though.

Any ideas/ best practices anyone would like to share? Thanks so much!