Error: convert-im6.q16: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/421.

Cause: Parsing PDF was disabled in /etc/ImageMagick-7/policy.xml due to its inherent insecurity. The same thing did Ubuntu and perhaps more distros will follow as this is recommendation from security researchers.

Fix: Enable it locally by removing 'PDF' from below line: <policy domain=“coder” rights=“none” pattern=“{PS,PS2,PS3,EPS,PDF,XPS}” />

File to edit: /etc/ImageMagick-7/policy.xml

Source: https://bugs.archlinux.org/task/60580