If index.html points to the Home Page, then that effectively becomes the default. If there is no index.html present, then the server will provide what is more or less a UNIX directory listing. This could include old versions of documents or ones not yet ready for release. Thus it is good practice to avoid this happening by including the link. Access to documents can be permitted or denied according to the network address of the Web Browser making the request.
Access control is based upon a per directory mechanism.
Create a separate directory. Place the document in it. Create a file called .htaccess in this directory with appropriate instructions. Create a link called index.html which points to the principal file which will be served by default. Restrictions defined in the control file apply to ALL documents in that directory.