Adobe acrobat reader is displaying the PDF source correctly.

I suggest to use ```pdftoppm -png -cropbox $$PDF$$ page```
instead of ```pdftoppm -png $$PDF$$ page```

This is in the default configuration of CommandLine and also in the help (_admin)

For more informations : https://www.normaprint.fr/blog/les-zones-de-page-pdf-n17
Actually we want to display the print area, what the user see in the viewer (crop box).

I suggest to wait to have more feedback about this modification before to apply it in the plugin.