check if pdf is downloaded

Hi, in an automation, I provide a link to a PDF document.

I want to set a tag when that document is actually opened/downloaded.

In FluentCRM, what is the best way to do this? With 'link click' benchmark or smartlink?
When I use benchmark, how can I prevent that my automation steps are skipped when someone clicks that link?

And with smartlink, can I set this straight to the (external) pdf file?