Quick one. When using Pandoc to create a PDF through the HTML interface, you can pass parameters to WKHTMLTOPDF via --enable-local-file-access. This is necessary when embedding Mermaid diagrams so it can export those to image, and then include them in the final PDF result. Not required on OSX, but is on Windows. Surprise.
pandoc -t html5 -f markdown 20200529-CreativeWorksModelling.md -o y.pdf --filter pandoc-mermaid --enable-local-file-access
(Pandoc, please convert my Markdown into a HTML5, then output that to PDF (y.pdf). While you're at it, any mermaid diagrams in there covert to images and include them in the output. thanks!)