Determine if your server is missing software for WordPress 4.7's native PDF thumbnail generator.
This will quickly tell your server has all the software installed to take advantage of WordPress 4.7’s built-in PDF thumbnail generation. Some plugins may shim the functionality in other ways. This test only concerns the native WordPress functionality.
From Sterner Stuff Design.
Tests:
* ImageMagick
* Imagick PECL Extension
* GhostScript
* Your WordPress Version
/wp-content/plugins/plugin-name
directory, or install the plugin through the WordPress plugins screen directly./wp-content/plugins/plugin-name
directory, or install the plugin through the WordPress plugins screen directly.Find this under Tools.
Congratulations! Other plugins may shim the functionality using other software. This is more useful for when things aren’t working.
Contact your hosting provider. Hopefully they can get what you need installed. Be sure to tell them exactly what you need.
Update your WordPress, either yourself or by contacting your website provider. WordPress updates include security patches, so you really should do this anyway.