No index and no follow on pdf with smartcrawl

I can not choose to no index and no follow pdf with smarcrawl. I have tried this in htaccess

<FilesMatch “.pdf$”>

header set x-robots-tag: noindex

</FilesMatch>

and also tried to add the following in robot.txt file

Disallow: /*.pdf

but it did not work, could you please share me a functional line of code to insert in the robot.txt file