If you have apache, you can use
Redirect 301 <old page> <new page>
Replace items inside brackets with actual values. Also, you typically have to use full path on the <new page> (i.e.,
http://...).
Keep in mind that if you do it this way you will not be able to access the file via http either. So you'll have to pull it down with FTP or something else.
Your other option would be to move it to a password protected directory.