S3 supports versioning of data - that is multiple copies of the same file can be stored in S3. Versioning can be enabled when a bucket is created or later. The versioning option is under the properties section of the bucket.
To enable versioning of an existing bucket, login to AWS and move to S3 console. Highlight the bucket and then click on properties.
Then the following screen is displayed
and then click on Versioning.
From this screen, the versioning can either be enabled or suspended. Note that when suspended, older versioned files will still exist and not be automatically deleted. Once Versioning is enabled, the status will appear on the properties screen.
So, the same or modified object is reuploaded, both version of the objects will exist. The latest upload is considered the latest version and will appear on the default S3 console. However, when the object is highlighted, there is a Latest version dropdown that will allow to download different versions of the object.
Note that from this screen, the different versions can be downloaded or deleted.