Convert PDF to PNG with enough resolution

ImageMagick logoAs ‘man convert’ states :

The convert program is a member of the ImageMagick suite of tools. Use it to convert between image formats as well as resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.

I use it to convert a pdf file to png picture with enough pixel density for the screen. This is the command :

convert -density 100 source.pdf target.png