Stirling-PDF: 92K-Star Open-Source PDF Toolbox – Free Local Alternative to Adobe/WPS

Why Stirling-PDF Exists

Common PDF tasks — merging files, converting to Word, adding e-signatures, compressing scans — are frequently locked behind paywalls in WPS, Adobe Acrobat, or ad-laden online services. Stirling-PDF addresses this by providing a fully open-source, locally deployed web application that offers 55+ PDF tools without subscriptions, watermarks, or mandatory uploads.

Core Highlights

GitHub: ~92K stars, one of the most popular self-hosted PDF projects.

Docker: Tens of millions of pulls; runs on NAS, servers, or personal computers.

Languages: 40+ fully supported, including mature Chinese UI.

Tools: 55+ utilities covering the vast majority of office PDF scenarios.

Privacy-first: Files never leave the machine; contracts, IDs, and confidential documents stay local.

One-sentence summary: Nearly every paid PDF feature on the market is free in Stirling-PDF, with the added benefit of private, on-premise deployment.

Feature Breakdown

1. Merge & Split (Highest-Frequency Need)

One-click merge of multiple PDFs with drag-and-drop reordering. Split by page range, file size, or extract single pages in batch. Also supports page deletion, reordering, rotation, crop, n-up (multiple pages per sheet), and content scaling.

Use cases: Tender document compilation, thesis chapter extraction, scanned archive pagination.

2. Bi-Directional Format Conversion

Leverages LibreOffice for PDF ↔ Word/Excel/PPT/Image conversion. Also exports HTML, Markdown, or live URLs to PDF, and PDF to XML/CSV.

Note: Office conversion requires LibreOffice; the ultra-lite Docker image excludes it, while the full image bundles it automatically.

Use cases: Editing PDF content, archiving reports, batch photo-to-PDF, web-page snapshots.

3. Compression for Attachment Limits

WeChat (25 MB) and email (10 MB) caps often block scanned PDFs. Stirling-PDF uses qpdf/Ghostscript with three presets: light (near-lossless), medium (significant size reduction), and extreme (best for text-only PDFs).

4. OCR — Privacy-Focused Killer Feature

Embedded Tesseract engine recognizes Chinese and produces a searchable, copyable text layer. Recognition happens entirely locally; no files are sent to external servers.

Setup: Requires Chinese language pack; mount the tessdata directory when using the full Docker image.

Use cases: Digitizing legacy paper archives, import/export document recognition, contract digitization.

5. E-Signatures, Certificate Signing & Sanitization

Handwritten signature via mouse/touchpad or uploaded image.

Certificate signing: auto-generate self-signed certs or import custom certificates for compliant digital seals.

Sanitize: strips metadata, hidden scripts, external links, embedded files — cleans privacy traces before distribution.

Redact: permanently deletes underlying text , not just visual masking; supports regex batch redaction for ID numbers, phone numbers, etc.

6. Security & Permission Management

Set open passwords and permission passwords (disable print, copy, edit). Also remove passwords, lock/unlock form fields.

7. Advanced Automation: Pipelines + REST API

Chain multiple steps into a pipeline — e.g., rotate → OCR → compress → watermark → encrypt — upload once, run automatically on batches. Full REST API enables Python scripts or internal system integration for programmatic batch processing.

8. V2 Major Updates

Frontend rewritten from Thymeleaf to React 19 + TypeScript + Vite (Mantine + Tailwind UI).

Undo/redo, multi-tool workspace — continuous operations without re-uploading.

PDF text editor (alpha): insert/replace text in simple documents; complex layouts may have compatibility issues.

Annotation tools: highlight, comment, draw, insert image/text boxes.

Enterprise features: user management, audit logs, SSO.

Native desktop apps via Tauri (Rust) for Windows, macOS, Linux — zero-config install.

Objective Limitations (Community-Reported)

Complex in-place text editing is limited — alpha editor only suits simple docs; Foxit/Adobe Pro remain better for heavy layout edits.

No AI-powered full-document translation — cannot one-click produce a translated PDF.

Cannot remove existing watermarks embedded in the source PDF.

Advanced features (OCR, Office conversion) depend on external binaries — ultra-lite image omits them; full image or manual install required.

Redaction deletes text at the binary level, but ultra-sensitive docs should still be double-checked.

Community reference: PDF24 for light use; PDFgear has niche strengths; Stirling-PDF wins on private deployment + batch pipelines + API.

Three Deployment Options

Option 1: Official Online Site (Quick Trial)

Visit stirlingpdf.com — no install, upload-process-download. Warning: Do not use for contracts, IDs, or sensitive files; online version uploads to the official server.

Option 2: Desktop Client (Recommended for Most Users)

Download the Tauri-packaged release (Windows/macOS/Linux). Double-click to run; bundles a minimal JRE. All processing stays local. macOS users needing OCR or Office conversion can install qpdf, tesseract, LibreOffice via Homebrew.

Option 3: Docker (NAS, Spare Hardware, Team Sharing — For Technical Users)

Quick start:

docker run -d --name stirling-pdf -p 8080:8080 -v ./stirling-data:/configs docker.stirlingpdf.com/stirlingtools/stirling-pdf:latest

Access at http://localhost:8080; any LAN device can connect.

Production docker-compose.yml with persistence:

version: '3.3'
services:
  stirling-pdf:
    image: stirlingtools/stirling-pdf:latest
    ports:
      - "8080:8080"
    volumes:
      - ./trainingData:/usr/share/tessdata
      - ./extraConfigs:/configs
      - ./logs:/logs
    environment:
      - DOCKER_ENABLE_SECURITY=false
      - LANGS=zh_CN,en_US
    restart: unless-stopped

Start with docker-compose up -d. Podman users replace docker with podman. Synology, UGREEN, TrueNAS, CasaOS offer one-click community packages.

Technical Architecture

Backend: Spring Boot (Java) + Apache PDFBox for core PDF operations; PDF.js and JPDFium for rendering/preview.

Frontend: React 19 + TypeScript + Vite, Mantine + Tailwind UI.

Desktop: Tauri (Rust).

AI/Advanced: Separate Python FastAPI engine.

External dependencies: LibreOffice (Office conversion), qpdf/Ghostscript (compression), Tesseract/OCRmyPDF (OCR), BouncyCastle (signing/crypto).

Architecture loads dependencies on demand; missing components simply hide the associated feature instead of crashing.

Selection Guide

Choose Stirling-PDF when:

You must process contracts, IDs, or classified PDFs locally — no third-party uploads.

You regularly batch-process PDFs and need pipelines or API automation.

You run a NAS/home server and want a shared PDF toolbox for family or a small team.

You want to stop paying WPS/Adobe subscriptions for everyday merge, split, compress, OCR, and e-sign tasks.

Avoid Stirling-PDF when:

You need heavy in-place editing of complex PDF layouts (prefer Foxit/Adobe).

You only want one-click removal of existing watermarks.

You require full-document AI translation with translated output.

Project Repository

https://github.com/Stirling-Tools/Stirling-PDF