This documentation is also published as Markdown for efficient machine reading: the whole site is indexed at /llms.txt, and every page has a clean Markdown copy at the same URL with .md appended. These are generated from the same source and cost far fewer tokens to read than this rendered HTML.

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June 12, 2026

Turn your docs into a PDF

By Phil Scott

You write your docs once as Markdown. Pennington.Book turns the same content into a downloadable PDF, without a second source of truth or an extra toolchain in your own project.

Defining books

You carve the navigation tree into books by route prefix. One line per area gives you a PDF whose slug lines up with that area; configure none and you get a single whole-site book:

csharp 
builder.Services.AddPenningtonBook(book =>
{
    book.Books.Add(new BookDefinition("Guides", "/how-to/"));
    book.Books.Add(new BookDefinition("Reference", "/reference/"));
});

There's no Use call. Registration is all of it. Each book reuses the render pipeline the live site uses: every page's HTML is converted back to Markdown and re-rendered (the same round trip llms.txt makes), then composed with a cover, a page-numbered table of contents, and a colophon. Print CSS and a paged.js polyfill are inlined, and images are embedded as data URIs, so the file stands on its own.

The dev server serves /pdf/{slug}.pdf on demand and a live /book-preview/{slug}/ for tuning the print CSS; the static build writes the PDFs alongside the HTML. On a DocSite, each area's sidebar grows a "Download as PDF" link automatically.

It needs a browser

The honest cost: the PDF is rendered by headless Chromium through PuppeteerSharp. On first run PuppeteerSharp downloads a private Chromium (around 150 MB) unless you point ChromiumExecutablePath at one you already have, and renders run one at a time. diag books prints each book's chapters and pages without launching Chromium at all, so you can check the structure cheaply. The generated-artifacts how-to explains how books fit the artifact tier.

pdfbooks