You can find the TYPO3 element Safe files (also known as the vault) under the tab Typical page content when creating a new content element. When you create links to your files via Safe files, they receive a URL where the file name does not appear.
If there are NO access restrictions set on a page, there will be no restrictions on the files in Safe files. If search engines have access to the page, they will also have access to the files.
Therefore, it is NOT enough to simply mark the page as not to be indexed, as this does not guarantee that the files will not be found. Access restriction and/or IP restriction are required. You can read about access restriction here og IP-restriction here (pkt. 5).
Before you start uploading files to Safe files, you should check the copyright. Read about copyright.