PDF to one image

convert in.pdf +append out%d.png

sudo apt install imagemagick

If convert is broken, update policy:

# Open the file 
sudo nano /etc/ImageMagick-6/policy.xml

# find and edit the line
<policy domain="coder" rights="none" pattern="PDF" />
# to :
<policy domain="coder" rights="read|write" pattern="PDF" />