Updating existing documents in the Media Library
When you need to amend a document that is stored in the Media Library, you need to update the original file on your hard drive, then go to the item in the Media Library, click on it to select it and then choose Modify. Then click 'Choose file' next to the Media field, browse to your amended file on your hard disk, just as you did when you added the original version of the item, and once it is uploaded, click Update.
If you have documents that need to be replaced with an updated version on a regular basis – eg programme brochures or specifications, module descriptions, application forms, or anything that includes a fee or cost that rises regularly – it may be very important that earlier versions are not left on the web server where they could be found in a search and give misleading information.
In this case, each time you upload a newer version, you need to be careful to save your updated file on your hard drive with exactly the same file name as the original one you added to the Media Library. This way the file on the server will be overwritten when it is published, and you will avoid any risk of out-of-date copies still being publicly available.