What are the htaccess mechanics of preventing search engines from indexing PDF files?

[dennis123]

What are the htaccess mechanics of preventing search engines from indexing PDF files?

[jesica]

The simplest way to prevent PDF documents from appearing in search results is to add an X-Robots-Tag: noindex in the HTTP header used to serve the file. If they're already indexed, they'll drop out over time if you use the X-Robot-Tag with the noindex directive.

[yuva12]

Using a “noindex” metatag. The most effective and easiest tool for preventing Google from indexing certain web pages is the “noindex” metatag. Basically, it's a directive that tells search engine crawlers to not index a web page, and therefore subsequently be not shown in search engine results.