Makeworthy Media

<p>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.</p>


Disable PDF Thumbnails

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

mbecher

<p>If your theme supports the thumbnail feature introduced in WordPress 2.9, this plugin will display attached thumbnails on the admin area’s manage posts and manage pages screen, similar to the media management page.</p>


Admin Thumbnails

If your theme supports Wordpress 2.9's thumbnail feature, this plugin displays thumbnails on the admin area's manage posts and manage pages  …

Disable PDF Thumbnails vs Admin Thumbnails