Raw Links are the actual URLs that our PDA Gold handles both original and private links. Although they look raw and ugly, Raw Links work on almost all hosting servers and platforms including Nginx and WordPress.org as they don't require server redirect.
Raw Protected File URL
Protected File URL: https://pda.com/wp-content/uploads/_pda/2018/12/sample-document.pdf vs
Raw version: https://pda.com/index.php?pda_v3_pf=/_pda/2018/12/sample-document.pdf
Raw Private URL
Private URL: https://pda.com/private/protected-file vs
Raw version: https://pda.com/index.php?pda_v3_pf=protected-file&pdav3_rexypo=ymerexy
These files are private, and so, not meant for SEO purposes. So Raw Links are a good fallback especially when your server doesn't allow rewrite rules modification.
As a matter of fact, using Raw Links actually speeds up the process of serving file (and file protection) as the file requests don't have to go through server rewrite rules (htaccess or Nginx redirects).