Makeworthy Media

Disables WordPress from generating image thumbnails when you upload a PDF. This behavior was introduced in WordPress 4.7, so this plugin isn’t needed for any version older than that. Not all web hosts support the ability to generate images from PDFs either, so even if you have 4.7 or newer you might not need this.

Disable PDF Thumbnails

Disables WordPress from generating image thumbnails when you upload a PDF.

fahrirusliyadi

WordPress generates thumbnails in the same directory with the original image. This plugin change this behavior by generating the thumbnails in a separate directory. The thumbnails will only be generated when they are needed and has not been generated.
This plugin will only move the thumbnails location for new uploaded images. To move all thumbnails, you need to delete all existing thumbnails (see FAQ).

Fr Thumbnails Folder

Move thumbnails file location to {$upload_path}/thumbnails or {$upload_path}/sites/{$blog_id}/thumbnails for multisite.

Disable PDF Thumbnails vs Fr Thumbnails Folder