Cloudflare Workers

Workers can’t compile WebAssembly at run time. Wrangler bundles the workerd export condition instead, which imports both .wasm files as WebAssembly.Modules. init instantiates them once per isolate.

This Worker returns a one-page letter at /?name=… and the 100-page report at /report. CI runs it in workerd (cargo xtask pdf-runtimes workerd):

packages/pdf/examples/worker/src/index.ts

// A Worker that generates a PDF per request: `/` a one-page letter for `?name=` (a 400 with the
// error as JSON for a name the standard font can't draw), `/report` the 100-page report with two
// embedded fonts (examples/report.ts). The fonts are this repository's fixtures; in your own
// Worker, bundle your font files the same way (wrangler.toml `rules`).
import { Builder, Font, init, isLaminaError, type LaminaError } from "@lamina/pdf";
import notoSans from "../../../../../fixtures/fonts/NotoSans-Regular.ttf";
import notoSansSC from "../../../../../fixtures/fonts/NotoSansSC-Regular.otf";
import { report } from "../../report.js";

/** The longest `?name=` the letter takes. */
const MAX_NAME = 100;

/**
 * A one-page letter to `name`, in a standard 14 font (nothing embedded, so only the characters
 * of its Latin character set: anything else throws `missing-glyph`).
 */
function letter(name: string): Uint8Array {
  const b = new Builder({ producer: "lamina Worker example" });
  try {
    const page = b.page("A4");
    page.surface().text(`Hello, ${name}!`, { font: Font.standard("Helvetica"), size: 24, at: [72, 96] });
    page.finish();
    return saveAndFree(b);
  } finally {
    // A no-op after finish(); when drawing threw, it frees the builder's WebAssembly side now
    // rather than whenever the garbage collector gets to it (an isolate serves many requests).
    b.free();
  }
}

/** Finishes `b`, saves the document and frees it (the bytes are a copy in JS memory). */
function saveAndFree(b: Builder): Uint8Array {
  const doc = b.finish();
  try {
    return doc.save();
  } finally {
    doc.free();
  }
}

const pdf = (bytes: Uint8Array): Response =>
  new Response(bytes as Uint8Array<ArrayBuffer>, { headers: { "content-type": "application/pdf" } });

/** Whether `e` is an error the name caused (see the `/` route). */
function isNameError(e: unknown): e is LaminaError {
  return isLaminaError(e) && (e.kind === "input" || e.kind === "limit");
}

/** A 400 with the error's ADR 0026 object as JSON. */
const badRequest = (body: unknown): Response => Response.json(body, { status: 400 });

// A default export because that is how a Worker module exposes its handlers (the named-exports
// rule is for package code).
export default {
  async fetch(request: Request): Promise<Response> {
    // Loads both modules once per isolate; later requests return at once.
    await init({ text: true });
    const url = new URL(request.url);
    switch (url.pathname) {
      case "/": {
        const name = url.searchParams.get("name") ?? "world";
        if (name.length > MAX_NAME) return badRequest({ message: `name is longer than ${MAX_NAME} characters` });
        try {
          return pdf(letter(name));
        } catch (e) {
          // A name Helvetica can't draw is the caller's input, not a server fault: a script it
          // lacks (`missing-glyph`, kind `input`: e.g. Cyrillic or Chinese) or more distinct
          // non-WinAnsi Latin letters than its 37 spare codes (`encoding-full`, kind `limit`).
          // Embed a font that covers them to accept them.
          if (isNameError(e)) return badRequest(e.toJSON());
          throw e;
        }
      }
      case "/report":
        // report() frees its builder and document itself.
        return pdf(report(new Uint8Array(notoSans), new Uint8Array(notoSansSC)));
      default:
        return new Response("not found", { status: 404 });
    }
  },
};

Its Wrangler configuration bundles the fonts as Data modules:

packages/pdf/examples/worker/wrangler.toml

# A Cloudflare Worker that generates a PDF per request with @lamina/pdf (B6c; the docs site's
# Worker example). `pnpm exec wrangler dev -c examples/worker/wrangler.toml` from packages/pdf.
# Wrangler bundles the `workerd` export condition, which imports both `.wasm` files as
# `WebAssembly.Module`s (Workers can't compile WebAssembly at run time).
name = "lamina-pdf-example"
main = "src/index.ts"
compatibility_date = "2026-10-01"

# The report's fonts are bundled with the Worker as ArrayBuffers.
[[rules]]
type = "Data"
globs = ["**/*.ttf", "**/*.otf"]
fallthrough = true

Run it locally from packages/pdf with pnpm exec wrangler dev -c examples/worker/wrangler.toml.

• Errors the caller caused (kind input or limit) become a 400 with the error’s JSON. See Errors and warnings.
• Memory: both functions free their builder and document as soon as the bytes are saved, because one isolate serves many requests.