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Self-Host Stirling PDF: Open Source PDF Tools 2026

·OSSAlt Team
stirling-pdfpdfself-hostingdockerocradobe-acrobat2026
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TL;DR

Stirling PDF (MIT, ~45K GitHub stars, Java) is a comprehensive self-hosted PDF manipulation tool with 50+ operations — merge, split, compress, convert, rotate, watermark, add page numbers, OCR, redact, sign, and more. Adobe Acrobat Standard costs $12.99/month ($155.88/year). Stirling PDF is free and processes everything locally — your documents never leave your server. It's become one of the most-starred self-hosted tools in 2025-2026 for good reason.

Key Takeaways

  • Stirling PDF: MIT, ~45K stars, Java — 50+ PDF operations in one self-hosted tool
  • No cloud uploads: All processing happens on your server — documents stay private
  • OCR: Built-in Tesseract OCR to make scanned PDFs text-searchable
  • Batch operations: Process multiple PDFs at once
  • API: Full REST API for automation (compress all PDFs from Paperless, etc.)
  • vs Adobe Acrobat: Stirling has most Acrobat features, free, no subscription

Feature Overview

CategoryOperations
OrganizeMerge, Split, Remove pages, Rotate, Reorder, PDF to single image per page
ConvertPDF→Word/Excel/PPT, Word/Excel/PPT→PDF, Image→PDF, PDF→Images, HTML→PDF
OptimizeCompress, Repair, Flatten annotations, Reduce file size
SecurityAdd/Remove passwords, Redact text, Add/Remove watermarks, Flatten forms
OtherOCR (text recognition), Add signatures, Add page numbers, Extract images, Extract text, Compare PDFs

Part 1: Docker Setup

# docker-compose.yml
services:
  stirling-pdf:
    image: frooodle/s-pdf:latest
    container_name: stirling-pdf
    restart: unless-stopped
    ports:
      - "8080:8080"
    volumes:
      - stirling_trainingData:/usr/share/tesseract-ocr/5/tessdata  # OCR language data
      - stirling_extraConfigs:/configs   # Custom configs
      - stirling_logs:/logs
      - stirling_customFiles:/customFiles
    environment:
      DOCKER_ENABLE_SECURITY: "false"  # Set true to enable login
      SECURITY_ENABLELOGIN: "false"
      LANGS: "en_GB"
      TZ: "America/Los_Angeles"
      # Enable OCR (downloads language data on first use):
      INSTALL_BOOK_AND_ADVANCED_HTML_OPS: "false"
      TESSERACT_LANGS: "eng"

volumes:
  stirling_trainingData:
  stirling_extraConfigs:
  stirling_logs:
  stirling_customFiles:

docker compose up -d

Visit http://your-server:8080

Part 2: HTTPS with Caddy

pdf.yourdomain.com {
    reverse_proxy localhost:8080
}

Part 3: Authentication (Optional)

For multi-user or internet-exposed deployments:

environment:
  DOCKER_ENABLE_SECURITY: "true"
  SECURITY_ENABLELOGIN: "true"
  SECURITY_INITIALLOGIN_USERNAME: "admin"
  SECURITY_INITIALLOGIN_PASSWORD: "your-admin-password"
  # Users can be managed in the UI after login

Part 4: Common Operations

Merge PDFs

  1. Merge/Split → Merge PDFs
  2. Upload multiple PDFs
  3. Drag to reorder
  4. Merge → download combined PDF

Split a PDF

  1. Merge/Split → Split PDF
  2. Upload PDF
  3. Choose: split by page ranges, split every N pages, split on specific pages
  4. Download as ZIP of split files

Compress PDF

  1. Other → Compress PDF
  2. Upload PDF
  3. Choose compression level (lower quality = smaller size)
  4. Download compressed PDF

OCR a scanned document

  1. Other → PDF OCR
  2. Upload scanned PDF (image-only)
  3. Select language: English
  4. Stirling runs Tesseract OCR
  5. Download text-searchable PDF
# Via API (for automation):
curl -X POST "https://pdf.yourdomain.com/api/v1/misc/ocr-pdf" \
  -H "Content-Type: multipart/form-data" \
  -F "fileInput=@scan.pdf" \
  -F "languages=eng" \
  --output scan-ocr.pdf

Redact sensitive information

  1. Security → Redact PDF
  2. Upload PDF
  3. Draw rectangles over sensitive areas (SSN, account numbers, etc.)
  4. Redact → areas permanently blacked out

Add passwords

  1. Security → Encrypt PDF
  2. Upload PDF
  3. Set owner password (full access) and user password (read-only)
  4. Encryption: AES-256
  5. Download encrypted PDF

Part 5: REST API

Full API for automation and integration with Paperless, n8n, etc.:

BASE="https://pdf.yourdomain.com/api/v1"

# Merge two PDFs:
curl -X POST "$BASE/general/merge-pdfs" \
  -H "Content-Type: multipart/form-data" \
  -F "fileInput=@doc1.pdf" \
  -F "fileInput=@doc2.pdf" \
  --output merged.pdf

# Compress a PDF:
curl -X POST "$BASE/general/compress-pdf" \
  -F "fileInput=@large.pdf" \
  -F "optimizeLevel=2" \
  --output compressed.pdf

# Convert PDF to images:
curl -X POST "$BASE/convert/pdf/img" \
  -F "fileInput=@document.pdf" \
  -F "imageFormat=png" \
  -F "singleOrMultiple=multiple" \
  --output images.zip

# Convert Word to PDF:
curl -X POST "$BASE/convert/file/pdf" \
  -F "fileInput=@document.docx" \
  --output document.pdf

# Extract text from PDF:
curl -X POST "$BASE/misc/extract-text" \
  -F "fileInput=@document.pdf" | jq '.text'

# Remove pages from PDF:
curl -X POST "$BASE/general/remove-pages" \
  -F "fileInput=@document.pdf" \
  -F "pageNumbers=1,3,5-7" \
  --output trimmed.pdf

n8n automation: compress all new PDFs

// n8n Code node — auto-compress PDFs from a watched folder:
const formData = new FormData();
formData.append('fileInput', items[0].binary.data);
formData.append('optimizeLevel', '2');

const response = await fetch('https://pdf.yourdomain.com/api/v1/general/compress-pdf', {
  method: 'POST',
  body: formData
});

return [{ binary: { data: await response.arrayBuffer() } }];

Part 6: Multi-Language OCR

Add more languages for OCR:

environment:
  TESSERACT_LANGS: "eng+fra+deu+spa+jpn"

Or install language packs manually:

# Download Tesseract language data:
docker exec stirling-pdf apt-get install -y \
  tesseract-ocr-fra \
  tesseract-ocr-deu \
  tesseract-ocr-spa

# Or copy .traineddata files to:
# /usr/share/tesseract-ocr/5/tessdata/

Available languages: 100+ via Tesseract's traineddata files.

Part 7: Pipeline Operations

Chain multiple operations together:

# Pipeline: compress → add page numbers → add watermark:
# Via UI: Other → Pipeline
# 1. Add Step: Compress PDF (level: 2)
# 2. Add Step: Add Page Numbers
# 3. Add Step: Add Watermark (text: "CONFIDENTIAL", opacity: 0.3)
# Run pipeline on uploaded file

Maintenance

# Update:
docker compose pull
docker compose up -d

# Check version:
curl https://pdf.yourdomain.com/api/v1/info

# Logs:
docker compose logs -f stirling-pdf

# Clear temporary files (auto-cleaned, but manual if needed):
docker exec stirling-pdf rm -rf /tmp/stirling-pdf-*

Why Self-Host Stirling PDF?

The case for self-hosting Stirling PDF comes down to three practical factors: data ownership, cost at scale, and operational control.

Data ownership is the fundamental argument. When you use a SaaS version of any tool, your data lives on someone else's infrastructure subject to their terms of service, their security practices, and their business continuity. If the vendor raises prices, gets acquired, changes API limits, or shuts down, you're left scrambling. Self-hosting Stirling PDF means your data and configuration stay on infrastructure you control — whether that's a VPS, a bare metal server, or a home lab.

Cost at scale matters once you move beyond individual use. Most SaaS equivalents charge per user or per data volume. A self-hosted instance on a $10-20/month VPS typically costs less than per-user SaaS pricing for teams of five or more — and the cost doesn't scale linearly with usage. One well-configured server handles dozens of users for a flat monthly fee.

Operational control is the third factor. The Docker Compose configuration above exposes every setting that commercial equivalents often hide behind enterprise plans: custom networking, environment variables, storage backends, and authentication integrations. You decide when to update, how to configure backups, and what access controls to apply.

The honest tradeoff: you're responsible for updates, backups, and availability. For teams running any production workloads, this is familiar territory. For individuals, the learning curve is real but the tooling (Docker, Caddy, automated backups) is well-documented and widely supported.

Server Requirements and Sizing

Before deploying Stirling PDF, assess your server capacity against expected workload.

Minimum viable setup: A 1 vCPU, 1GB RAM VPS with 20GB SSD is sufficient for personal use or small teams. Most consumer VPS providers — Hetzner, DigitalOcean, Linode, Vultr — offer machines in this range for $5-10/month. Hetzner offers excellent price-to-performance for European and US regions.

Recommended production setup: 2 vCPUs with 4GB RAM and 40GB SSD handles most medium deployments without resource contention. This gives Stirling PDF headroom for background tasks, caching, and concurrent users while leaving capacity for other services on the same host.

Storage planning: The Docker volumes in this docker-compose.yml store all persistent Stirling PDF data. Estimate your storage growth rate early — for data-intensive tools, budget for 3-5x your initial estimate. Hetzner Cloud and Vultr both support online volume resizing without stopping your instance.

Operating system: Any modern 64-bit Linux distribution works. Ubuntu 22.04 LTS and Debian 12 are the most commonly tested configurations. Ensure Docker Engine 24.0+ and Docker Compose v2 are installed — verify with docker --version and docker compose version. Avoid Docker Desktop on production Linux servers; it adds virtualization overhead and behaves differently from Docker Engine in ways that cause subtle networking issues.

Network: Only ports 80 and 443 need to be publicly accessible when running behind a reverse proxy. Internal service ports should be bound to localhost only. A minimal UFW firewall that blocks all inbound traffic except SSH, HTTP, and HTTPS is the single most effective security measure for a self-hosted server.

Backup and Disaster Recovery

Running Stirling PDF without a tested backup strategy is an unacceptable availability risk. Docker volumes are not automatically backed up — if you delete a volume or the host fails, data is gone with no recovery path.

What to back up: The named Docker volumes containing Stirling PDF's data (database files, user uploads, application state), your docker-compose.yml and any customized configuration files, and .env files containing secrets.

Backup approach: For simple setups, stop the container, archive the volume contents, then restart. For production environments where stopping causes disruption, use filesystem snapshots or database dump commands (PostgreSQL pg_dump, SQLite .backup, MySQL mysqldump) that produce consistent backups without downtime.

For a complete automated backup workflow that ships snapshots to S3-compatible object storage, see the Restic + Rclone backup guide. Restic handles deduplication and encryption; Rclone handles multi-destination uploads. The same setup works for any Docker volume.

Backup cadence: Daily backups to remote storage are a reasonable baseline for actively used tools. Use a 30-day retention window minimum — long enough to recover from mistakes discovered weeks later. For critical data, extend to 90 days and use a secondary destination.

Restore testing: A backup that has never been restored is a backup you cannot trust. Once a month, restore your Stirling PDF backup to a separate Docker Compose stack on different ports and verify the data is intact. This catches silent backup failures, script errors, and volume permission issues before they matter in a real recovery.

Security Hardening

Self-hosting means you are responsible for Stirling PDF's security posture. The Docker Compose setup provides a functional base; production deployments need additional hardening.

Always use a reverse proxy: Never expose Stirling PDF's internal port directly to the internet. The docker-compose.yml binds to localhost; Caddy or Nginx provides HTTPS termination. Direct HTTP access transmits credentials in plaintext. A reverse proxy also centralizes TLS management, rate limiting, and access logging.

Strong credentials: Change default passwords immediately after first login. For secrets in docker-compose environment variables, generate random values with openssl rand -base64 32 rather than reusing existing passwords.

Firewall configuration:

ufw default deny incoming
ufw allow 22/tcp
ufw allow 80/tcp
ufw allow 443/tcp
ufw enable

Internal service ports (databases, admin panels, internal APIs) should only be reachable from localhost or the Docker network, never directly from the internet.

Network isolation: Docker Compose named networks keep Stirling PDF's services isolated from other containers on the same host. Database containers should not share networks with containers that don't need direct database access.

VPN access for sensitive services: For internal-only tools, restricting access to a VPN adds a strong second layer. Headscale is an open source Tailscale control server that puts your self-hosted stack behind a WireGuard mesh, eliminating public internet exposure for internal tools.

Update discipline: Subscribe to Stirling PDF's GitHub releases page to receive security advisory notifications. Schedule a monthly maintenance window to pull updated images. Running outdated container images is the most common cause of self-hosted service compromises.

Troubleshooting Common Issues

Container exits immediately or won't start

Check logs first — they almost always explain the failure:

docker compose logs -f stirling-pdf

Common causes: a missing required environment variable, a port already in use, or a volume permission error. Port conflicts appear as bind: address already in use. Find the conflicting process with ss -tlpn | grep PORT and either stop it or change Stirling PDF's port mapping in docker-compose.yml.

Cannot reach the web interface

Work through this checklist:

  1. Confirm the container is running: docker compose ps
  2. Test locally on the server: curl -I http://localhost:PORT
  3. If local access works but external doesn't, check your firewall: ufw status
  4. If using a reverse proxy, verify it's running and the config is valid: caddy validate --config /etc/caddy/Caddyfile

Permission errors on volume mounts

Some containers run as a non-root user. If the Docker volume is owned by root, the container process cannot write to it. Find the volume's host path with docker volume inspect VOLUME_NAME, check the tool's documentation for its expected UID, and apply correct ownership:

chown -R 1000:1000 /var/lib/docker/volumes/your_volume/_data

High resource usage over time

Memory or CPU growing continuously usually indicates unconfigured log rotation, an unbound cache, or accumulated data needing pruning. Check current usage with docker stats stirling-pdf. Add resource limits in docker-compose.yml to prevent one container from starving others. For ongoing visibility into resource trends, deploy Prometheus + Grafana or Netdata.

Data disappears after container restart

Data stored in the container's writable layer — rather than a named volume — is lost when the container is removed or recreated. This happens when the volume mount path in docker-compose.yml doesn't match where the application writes data. Verify mount paths against the tool's documentation and correct the mapping. Named volumes persist across container removal; only docker compose down -v deletes them.

Keeping Stirling PDF Updated

Stirling PDF follows a regular release cadence. Staying current matters for security patches and compatibility. The update process with Docker Compose is straightforward:

docker compose pull          # Download updated images
docker compose up -d         # Restart with new images
docker image prune -f        # Remove old image layers (optional)

Read the changelog before major version updates. Some releases include database migrations or breaking configuration changes. For major version bumps, test in a staging environment first — run a copy of the service on different ports with the same volume data to validate the migration before touching production.

Version pinning: For stability, pin to a specific image tag in docker-compose.yml instead of latest. Update deliberately after reviewing the changelog. This trades automatic patch delivery for predictable behavior — the right call for business-critical services.

Post-update verification: After updating, confirm Stirling PDF is functioning correctly. Most services expose a /health endpoint that returns HTTP 200 — curl it from the server or monitor it with your uptime tool.

See all open source PDF and productivity tools at OSSAlt.com/categories/productivity.

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