I did a small python program to generate a pdf file (with one or two pages) from a kicad pcb file, which contains files for DIY fabrication (copper and masks layers). By default copper layers are negative, masks are not, and Top layers are always mirrored. The biggest feature of the code is to combine artworks on a pdf page, to avoid wasting transparent sheets. It’s a python command line tool, you can change a few options the classic way (--no-mask for example), use -h to get all the options.
You can get more explanations on the Gitlab snippet page.
Ouput of example above with default options (Forums rules didn’t allow me to post two pictures at the same time).
I do not know if this could have been done entirely with the Kicad Python API instead of muddling through pdf manipulations, but maybe this could be of use for a plugin like Kikit
Nice work. I probably won’t use it because I don’t make my own boards, but I do have a quality of life upgrade that you might consider. When generating the PDF, include the layer name under/near each layer graphic so one remembers which layer is which after printing. The mask vs copper is easy enough to identify, but I can see forgetting which is top and bottom easily.
Maybe have the text mirrored such that it is “right reading” when oriented properly for the lithography process (emulsion/toner side against copper).