SVG was mentioned (as spec'd by w3.org IIRC).
So check out Inkscape:
"using the W3C standard Scalable Vector Graphics (SVG) file format."
Available for multiple platforms.
Using an open format that requires people to install special free software
is no different than using a proprietary format that requires people
to install special free software. And if that is to be the case, PDF
is much more widespread than SVG.
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