PDF Processing in JavaScript: pdf-lib vs pdf-parse vs pdfjs-dist

Working with PDFs in web applications is notoriously tricky due to the format’s complexity. The three main libraries—pdf-lib, pdf-parse, and pdfjs-dist—address different parts of the problem: authoring, text extraction, and rendering/inspection. Understanding their roles prevents costly architectural missteps.

📝 Core Purpose: What Each Library Actually Does

pdf-lib: PDF Authoring and Modification

pdf-lib treats PDFs as editable documents. You can:

• Create new PDFs from scratch
• Embed fonts and draw text/graphics
• Merge, split, or rearrange pages
• Fill AcroForm fields or add annotations

It operates on the PDF’s internal structure (objects, streams, cross-reference tables) but does not render pages visually or interpret layout for text extraction.

// pdf-lib: Create a new PDF and add text
import { PDFDocument, StandardFonts } from 'pdf-lib';

const pdfDoc = await PDFDocument.create();
const page = pdfDoc.addPage([500, 300]);
const font = await pdfDoc.embedFont(StandardFonts.Helvetica);
page.drawText('Hello from pdf-lib!', { x: 50, y: 250, size: 20, font });
const pdfBytes = await pdfDoc.save(); // Uint8Array

pdf-parse: Simple Text Extraction (Node.js Only)

pdf-parse is a thin wrapper around pdfjs-dist that only extracts raw text from a PDF buffer. It returns a string with all text concatenated, stripped of formatting, positioning, or structure. It’s synchronous in spirit (returns a Promise) but offers no control over parsing behavior.

// pdf-parse: Extract plain text (Node.js only)
import pdf from 'pdf-parse';
import fs from 'fs';

const pdfBuffer = fs.readFileSync('document.pdf');
const data = await pdf(pdfBuffer);
console.log(data.text); // "All text concatenated into one string"

⚠️ Note: pdf-parse is not usable in browsers because it relies on Node.js Buffer objects and doesn’t expose PDF.js’s rendering APIs.

pdfjs-dist: Full PDF Rendering and Analysis

pdfjs-dist is Mozilla’s battle-tested PDF engine. It can:

• Render pages to <canvas> or <svg> for display
• Extract text with character positions and bounding boxes
• Parse document metadata, outlines, and attachments
• Handle encrypted or password-protected files

It’s the foundation for Firefox’s built-in PDF viewer and works in both browser and Node.js (with polyfills).

// pdfjs-dist: Render first page to canvas (browser)
import * as pdfjsLib from 'pdfjs-dist';

// Set worker path (required)
pdfjsLib.GlobalWorkerOptions.workerSrc = './pdf.worker.js';

const loadingTask = pdfjsLib.getDocument('document.pdf');
const pdf = await loadingTask.promise;
const page = await pdf.getPage(1);

const canvas = document.getElementById('pdf-canvas');
const viewport = page.getViewport({ scale: 1.5 });
canvas.height = viewport.height;
canvas.width = viewport.width;

const renderContext = { canvasContext: canvas.getContext('2d'), viewport };
await page.render(renderContext).promise;

🔍 Text Extraction: Raw vs Structured

When you need to pull text out of a PDF, the approach varies drastically.

pdf-lib cannot extract text. It reads PDF structure but doesn’t interpret content streams as human-readable text.

pdf-parse gives you a blob of text with no layout info:

// pdf-parse output example
"Title\nSection 1\nThis is paragraph one.\nSection 2\nAnother paragraph."

pdfjs-dist provides structured text with positioning, which lets you reconstruct reading order or detect columns:

// pdfjs-dist: Get text with layout info
const page = await pdf.getPage(1);
const textContent = await page.getTextContent();

// textContent.items = [
//   { str: "Title", transform: [1, 0, 0, 1, 50, 700], ... },
//   { str: "Section 1", transform: [1, 0, 0, 1, 50, 680], ... }
// ]

const text = textContent.items.map(item => item.str).join(' ');

If you need to know where text appears on the page (for redaction, search highlighting, or data scraping), only pdfjs-dist delivers.

🖼️ Rendering PDFs for Display

Only pdfjs-dist can render PDFs visually. Neither pdf-lib nor pdf-parse has any rendering capability.

In the browser, pdfjs-dist draws pages to <canvas> with high fidelity, including vector graphics, embedded fonts, and transparency. You can also render to SVG for scalable output.

// pdfjs-dist: Render to SVG (alternative to canvas)
const operatorList = await page.getOperatorList();
const svgGraphics = await pdfjsLib.SVGGraphics.init(page.commonObjs, page.objs);
const svg = await svgGraphics.paintSvg(operatorList);
document.body.appendChild(svg);

Attempting to use pdf-lib for display will fail—it outputs byte arrays, not renderable DOM elements.

⚙️ Environment Support and Dependencies

* Node.js usage requires polyfills for window, document, etc., and careful bundler configuration.

pdfjs-dist’s worker requirement in browsers is non-negotiable for performance—it offloads parsing to a Web Worker to avoid blocking the UI thread. You must host pdf.worker.js and set GlobalWorkerOptions.workerSrc.

pdf-parse bundles pdfjs-dist but hides this complexity, at the cost of flexibility.

🛠️ Real-World Decision Guide

Scenario 1: Generate Invoices in the Browser

You need to create PDF invoices from user data and let them download it.

• ✅ Use pdf-lib: It generates PDFs client-side with custom fonts, tables, and logos.
• ❌ Avoid pdfjs-dist: Overkill—you don’t need rendering.
• ❌ Avoid pdf-parse: Can’t create PDFs.

Scenario 2: Build a PDF Viewer Component

Users upload PDFs and view them page-by-page in your app.

• ✅ Use pdfjs-dist: Only it can render pages accurately.
• ❌ Avoid others: Neither renders visuals.

Scenario 3: Extract Text from Uploaded PDFs (Backend)

Your server receives PDFs and needs to index their content for search.

• If you only need raw text → pdf-parse (simplest API)
• If you need layout-aware text (e.g., to detect tables) → pdfjs-dist directly
• ❌ Never pdf-lib: No text extraction

Scenario 4: Add Watermarks to Existing PDFs

Stamp “CONFIDENTIAL” on every page of a user-uploaded document.

• ✅ Use pdf-lib: Load the PDF, iterate pages, draw text overlay, save.
• ❌ Avoid pdfjs-dist: Can’t modify document structure.
• ❌ Avoid pdf-parse: Read-only.

🧩 API Complexity and Learning Curve

• pdf-lib: Moderate. You work with pages, fonts, and drawing commands. Documentation is clear with examples for common tasks.
• pdf-parse: Very low. One function, one promise, one string result.
• pdfjs-dist: High. You manage document loading, page retrieval, rendering contexts, and worker setup. The API exposes PDF internals (operator lists, transforms, glyphs).

For quick text extraction in Node.js, pdf-parse wins on simplicity. For anything involving modification or rendering, you’ll invest time learning the chosen library’s model.

🔄 Interoperability

These libraries don’t interoperate directly, but you can chain them in workflows:

1. Use pdfjs-dist in the browser to render a PDF for preview
2. Send the same PDF to your Node.js backend
3. Use pdf-lib to add a signature page
4. Use pdf-parse to extract text for archival

However, note that pdf-lib and pdfjs-dist parse PDFs differently—they may not agree on page count or structure if the PDF is malformed.

💡 Summary: When to Use Which

Choose based on whether you’re writing (pdf-lib), reading for display (pdfjs-dist), or reading for text only (pdf-parse). Mixing them is possible but adds bundle size—avoid unless necessary.