If you need to redirect .pdf file link to certain page u can write code below on .htaccess file

For .htaccess file

In the root of your documents folder of the webserver, place a new .htaccess file (or modify the existing one, if you’ve already created one in the past).

Redirect 301 /pdf/some-document.pdf http://example.com/some-document.pdf

But dont forget its depends on your web server or app server, whatever.