Libpdf Helper

LibPDF Helper

Comprehensive guidance for using @libpdf/core (v0.2.5), a modern TypeScript PDF library that parses, modifies, and generates PDFs.

What is @libpdf/core?

A production-ready PDF library combining:

• Lenient parsing like PDFBox and PDF.js (opens malformed PDFs)
• Intuitive API like pdf-lib (TypeScript-first, clean)
• Complete features: encryption, digital signatures (PAdES), incremental saves, forms, text extraction

Key differentiators:

• Opens documents other libraries reject (brute-force recovery fallback)
• Incremental saves preserve digital signatures
• Full PAdES signature support (B-B, B-T, B-LT, B-LTA)
• Universal runtime (Node.js 20+, Bun, browsers)

When to Use vs Alternatives

Migrate when:

• pdf-lib fails on malformed PDFs
• Need digital signatures or incremental saves
• Need complete feature set (encryption, attachments, text extraction)

Workflows

1. Migrating from Another Library

Read the appropriate migration guide:

• From pdf-lib: references/migration-from-pdf-lib.md (most common)
• From pdf.js: references/migration-from-pdfjs.md (when adding modification)
• From pdfkit: references/migration-from-pdfkit.md (when adding parsing)

Guides show side-by-side code comparisons for easy translation.

2. Finding Solutions for Specific Tasks

Option A: Browse by category in references/use-cases-by-category.md

• 12 categories matching common PDF tasks
• Each entry: when to use + code snippet + example reference

Option B: Check the examples directory with working implementations:

01-basic/              Creating, loading, saving
02-pages/              Add, remove, copy, rotate pages
03-forms/              Fill, flatten, create fields
04-drawing/            Text, shapes, paths, custom content
05-images-and-fonts/   Embed images, fonts, subsetting
06-metadata/           Title, author, keywords, dates
07-signatures/         Digital signatures, PAdES, LTV
08-attachments/        Embed and extract files
09-merging-and-splitting/ Combine or split PDFs
10-security/           Encryption, permissions, passwords
11-advanced/           Incremental saves, low-level API
12-text-extraction/    Extract and search text

3. Quick API Reference

See references/api-quick-reference.md for:

• Common patterns by task
• Minimal working examples
• Key method signatures

Key Concepts

Two API Layers

High-level (use 95% of the time):

const pdf = await PDF.load(bytes);
const form = pdf.getForm();
form.fill({ name: "Jane" });
await pdf.save();

Low-level (for full control):

const catalog = pdf.context.catalog;
const pagesDict = catalog.get("Pages") as PdfDict;
// Work with PDF objects directly (PdfDict, PdfArray, PdfStream)

Incremental Saves

Critical for preserving digital signatures:

const signed = await pdf.save({ incremental: true });

Without incremental: true, signatures become invalid. The library automatically uses incremental saves when modifying signed PDFs.

Lenient Parsing

Opens malformed PDFs that strict parsers reject:

• Recovers xref tables by scanning entire file
• Tolerates incorrect offsets and object numbers
• Handles missing or malformed trailers

Falls back to brute-force when standard parsing fails.

Installation

npm install @libpdf/core
# or
bun add @libpdf/core

Requirements:

• Node.js 20+ (or Bun)
• TypeScript 5+ (recommended)
• Modern browser with Web Crypto API (for browser usage)

Quick Examples

Load and inspect:

import { PDF } from "@libpdf/core";
const pdf = await PDF.load(bytes);
console.log(`${pdf.getPageCount()} pages`);

Fill form:

const form = pdf.getForm();
form.fill({ name: "Jane", email: "jane@example.com", agreed: true });
await pdf.save();

Sign document:

import { P12Signer } from "@libpdf/core";
const signer = await P12Signer.create(p12Bytes, "password");
const signed = await pdf.sign({ signer, reason: "I approve" });

Merge PDFs:

const merged = await PDF.merge([pdf1Bytes, pdf2Bytes, pdf3Bytes]);

Extract text:

const text = pdf.getPage(0).extractText();
const results = pdf.getPage(0).findText(/invoice #\d+/gi);

Resources

• Documentation: https://libpdf.dev
• GitHub: https://github.com/LibPDF-js/core
• Examples: examples/ (12 categories)
• Issues: https://github.com/LibPDF-js/core/issues

Known Limitations

• Signature verification not yet implemented (signing works)
• TrueType Collections (.ttc) not supported
• JBIG2 and JPEG2000 images passthrough only (preserved but not decoded)
• Certificate encryption not supported (password encryption works)
• JavaScript form calculations ignored

These limitations affect edge cases; core features are production-ready.