Folders are an easy way to keep documents organized. Additionally, folders can be placed on pages to make updating file links quick and easy.
Go to Content > Media Manager > Documents.
Click Add a File.
Enter a display name for a file.
Update Restrictions, if appropriate.
Select "Create New Folder" from the Subfolder drop-down and update the "New Subfolder name" field with the folder name. If the folder already exists, select it from the "Subfolder" drop-down.