Plotting to PDF with the negative option only adds a black box around the PCB

Hi there,
I wanted to export/plot a design in kiCad to PDF, to print it out.

When plotting one layer and selecting the invert option, only a square around the design is generated (this is something I do want), the rest of the page is left white. Is there an option Iā€™m missing somewhere to blacken everything except the inverted parts and not only a square around it?

Any help is appreciated!