Getting Started

Installation

Install modern-pdf-lib with your preferred package manager:

npm

npm install modern-pdf-lib

pnpm

pnpm add modern-pdf-lib

bun

bun add modern-pdf-lib

deno

deno add npm:modern-pdf-lib

NOTE

modern-pdf-lib is ESM-only. It requires Node 25.7 or later, or any runtime with native ES module support.

Supported Runtimes

Runtime	Minimum Version	Notes
Node.js	25.7+	Full support including WASM acceleration
Deno	Latest	Full support via npm: specifier
Bun	Latest	Full support
Cloudflare Workers	—	Streaming output, no file system
Browsers	ES2024+	All modern browsers via bundler

Your First PDF

Create a simple "Hello World" PDF in just a few lines:

import { createPdf, PageSizes, rgb } from 'modern-pdf-lib';

const pdf = createPdf();
const page = pdf.addPage(PageSizes.A4);

page.drawText('Hello, Modern PDF!', {
  x: 50,
  y: 700,
  size: 24,
  color: rgb(0.1, 0.1, 0.1),
});

const bytes = await pdf.save();

The bytes variable is a Uint8Array containing a valid PDF document.

Running in Node

Write the PDF to a file using the Node fs module:

import { writeFile } from 'node:fs/promises';
import { createPdf, PageSizes, rgb } from 'modern-pdf-lib';

const pdf = createPdf();
const page = pdf.addPage(PageSizes.A4);

page.drawText('Hello from Node!', {
  x: 50,
  y: 700,
  size: 24,
  color: rgb(0, 0, 0),
});

const bytes = await pdf.save();
await writeFile('output.pdf', bytes);
console.log('Wrote output.pdf');

You can also stream the output directly to a file to reduce peak memory usage:

import { createWriteStream } from 'node:fs';
import { Writable } from 'node:stream';

const stream = pdf.saveAsStream();
const fileStream = createWriteStream('output.pdf');

await stream.pipeTo(Writable.toWeb(fileStream));

Running in the Browser

In a browser context you can trigger a download or display the PDF in an iframe:

import { createPdf, PageSizes, rgb } from 'modern-pdf-lib';

const pdf = createPdf();
const page = pdf.addPage(PageSizes.A4);

page.drawText('Hello from the browser!', {
  x: 50,
  y: 700,
  size: 24,
  color: rgb(0, 0, 0),
});

const blob = await pdf.saveAsBlob();
const url = URL.createObjectURL(blob);

// Trigger a download
const a = document.createElement('a');
a.href = url;
a.download = 'document.pdf';
a.click();

// Clean up
URL.revokeObjectURL(url);

Running in Cloudflare Workers

Return the PDF as a streaming HTTP response:

import { createPdf, PageSizes, rgb } from 'modern-pdf-lib';

export default {
  async fetch(): Promise<Response> {
    const pdf = createPdf();
    const page = pdf.addPage(PageSizes.A4);

    page.drawText('Hello from Workers!', {
      x: 50,
      y: 700,
      size: 24,
      color: rgb(0, 0, 0),
    });

    const stream = pdf.saveAsStream();

    return new Response(stream, {
      headers: {
        'Content-Type': 'application/pdf',
        'Content-Disposition': 'attachment; filename="document.pdf"',
      },
    });
  },
};

WASM Initialization

modern-pdf-lib ships with optional WebAssembly modules that accelerate compression, PNG decoding, font parsing, and text shaping. Without WASM, the library falls back to pure-JavaScript implementations.

How It Works

WASM modules are not loaded automatically — you must explicitly initialize them by passing pre-compiled WebAssembly.Module instances or by specifying which modules to load. Without WASM, the library uses pure-JS fallbacks that produce identical output.

import { initWasm } from 'modern-pdf-lib';

// Load specific WASM modules during app startup
await initWasm({ deflate: true, png: true, fonts: true });

// All subsequent operations use WASM-accelerated paths
const bytes = await pdf.save();

You can also provide custom paths to the .wasm files if your deployment requires specific asset locations:

await initWasm({
  deflateWasm: new URL('./wasm/deflate.wasm', import.meta.url),
  pngWasm: new URL('./wasm/png.wasm', import.meta.url),
});

TIP

WASM acceleration is entirely optional. The pure-JS fallback produces identical PDFs — just slightly slower for large documents.

Next Steps

• Text Drawing — Fonts, sizes, colors, and positioning
• Images — Embed PNGs and JPEGs
• Fonts — Custom fonts, subsetting, and complex scripts
• Shapes — Rectangles, circles, lines, and colors
• Streaming — Memory-efficient output for large documents
• API Reference — Full TypeDoc-generated reference