Maintaining a history of document versions is an option that can be set for each document library. The default setting is to disable maintenance of the document's version history. The following are the steps to follow to enable version history:
From inside of the document library click on Modify Settings and Columns in the Quick Launch area.
Click on Change General Settings.
Scroll down to Document Versions and change the option to Yes.
Click on OK to save the changes.
If document versions is enabled, each time a document is saved the previous version is also saved. Versions are useful to have if the documents are valuable and it is important to be able to recover in the event of an inadvertent ...