Marcin Kijak

After installation you can find “Noindex by path” option in the main menu. This allows you to simply add relative paths 
you need to exclude from SERPs. Add a path (including slashes from begging and the end of the string) and save the 
changes. Since this plugin is called to be “simple” you can add only one path at once, but the process is smooth 
and easy.
Plugin will add “noindex” meta tag which is an instruction for search engines that this particular page should not be indexed. 
Technically it modifies wp_head tag.

Noindex by Path

Ask search engines not to index individual pages by a relative path - which means you can set every url no matter it is a page, category listing or an …

Rahul Mondal

No-Indexer is a WordPress plugin that allows you to add a checkbox in all page and post settings sidebar to set a noindex meta tag for specific pages and also the pages exclude from robots.txt and sitemap.xml.
<h3>Usage</h3>
<ol>
<li>After activating the plugin, go to the edit page screen for any page.</li>
<li>In the page settings sidebar, you will find a checkbox labeled “Noindex this page”.</li>
<li>Check the checkbox if you want to add a noindex meta tag to the page.</li>
<li>Update or publish the page to apply the changes.</li>
</ol>

No-Indexer

Add a checkbox in page, post, and custom type settings to instruct search engines not to index the content, excluding it from robots.txt and sitemap.

Noindex by Path vs No-Indexer