Why the PDF is a bitmap, and how to get vector output

What is in the PDF

“Export PDF” produces a single-page PDF: the page is the size of the diagram, the background follows the current theme, and the content is a PNG at 3x resolution. It prints clearly on A4 and has no header, footer or watermark.

The original Mermaid code is stored in the PDF's document properties (the “Subject” field), where any PDF reader can show and copy it.

Why not vector

A vector PDF has to embed fonts. Even a minimal CJK subset weighs several megabytes, has to be downloaded, and would not match the system fonts used in the preview, so the diagram would look different. The bitmap route needs no network, uploads nothing, and matches the preview exactly, which is a rule Diagramate does not bend.

When you need vector

• Export SVG: it is vector already. Browsers, Illustrator, Inkscape and Figma open it, and can convert it to a vector PDF.
• For LaTeX, use SVG or the 3x PNG.

Very large diagrams

PDF pages have a maximum side length (about 5 metres). Larger diagrams are scaled to fit the limit while keeping the pixels; print at scale.