We want to add some file fields to individual contacts for PDF documents. Is there a way to store these files so that they can be accessed by a Civicrm user with appropriate permissions but not reachable on the web site otherwise - including by a search bot or similar agent that may ignore a robots.txt instruction? I realize this question may go beyond Civicrm configuration to web server security in general but hoping someone can point me in the right direction. My civicrm is running on WordPress on Ubuntu. Thanks.