The revisioning system is Drupal’s built-in versioning system. It enables to store the different versions and all adjustments made of every node.
Proceed as follows to create an update of an existing node and to save that update as a new version of the node.
Go to Administer > Content in the administrator toolbar.
If necessary, use the filter to narrow down the results list.
Select the node that needs updating and click on Edit in the Operations column.
Make the required changes in the node.
Make sure the option checkbox Create new revision in Revision information has been checked in order to store a new version of this node.
Add comments to the changes in the Log message text field.
Click on Save to save the changes.