How to install imagemagick for php7 on Ubuntu?
Creating and displaying preview images of PDF files relies on these packages that need to be installed on your server :
- ImageMagick
- Imagick
- Ghostscript
To install all of these modules run:
sudo apt-get install php-imagick
To make the change take effect, restart Apache:
sudo service php7.0-fpm reload
More details in this article:
Using the New PDF Preview Images in WordPress 4.7 in the Real World