Since version 4.7 it is possible to let WordPress generate preview images for uploaded PDF documents. Therefore, your server has to meet the following requirements:
- Imagick.
- ImageMagick.
- Ghostscript.
You have to install Imagick — ImageMagick and Ghostscript are installed by default. To retrofit Imagick, you just need to run the following command on the shell and can enjoy PDF preview images for new uploads:
uberspace-install-pecl imagick