Convert Markdown to PDF

Markdown exists because writing should not require a word processor, and it succeeds so completely that a great deal of real documentation, specifications and notes now live as .md files. The awkward moment comes when one of them has to be sent to somebody who does not want a text file — a client, a regulator, a committee — and needs to arrive as a document.

This converts one to the other, and the interesting decisions are all about scope.

The parser recognises exactly what the layout engine can draw: headings, paragraphs, bullet and numbered lists, block quotes, fenced and indented code, horizontal rules, and links. That correspondence is deliberate and it is the most important property of the tool. A parser that recognised tables while the renderer ignored them would produce silent data loss — a table in your source, a blank space in your PDF, and nothing anywhere to say so. Instead, anything unsupported comes through as the text it was written as. Pipes and asterisks in the output are ugly; content that quietly vanished is worse, because you find out about it later and from somebody else.

Code gets the most careful handling, because code is what most of these documents are full of. A fenced block is taken verbatim — nothing inside it is interpreted, so an asterisk in a shell command stays an asterisk — and drawn in a monospaced face with its indentation intact, since in code the indentation carries the meaning. A line too long for the page is wrapped rather than clipped off the edge.

Inline emphasis is stripped rather than rendered, and that is the one omission likely to disappoint. Changing weight partway through a line means measuring and drawing each run separately and keeping it correct across line wrapping and page breaks, which is a genuinely larger piece of work than it appears from the outside. Supporting it in some positions and not others would be worse than not supporting it, so the markers are removed and the words read cleanly. Headings carry most of a document's emphasis anyway, and they are drawn bold at real sizes.

Images are not fetched. A reference becomes its alt text and its path, which tells you what was there. Embedding them would mean either reaching into your filesystem or making network requests for remote ones — and a tool that promises your document never leaves the tab cannot start making requests on its behalf.

The layout engine is shared with Create PDF, so the two produce documents that look like they came from the same place. The difference between the pages is only whether your text is interpreted: this one reads Markdown, that one reads nothing at all, which is what you want when what you are pasting is an email or a log.