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Stirling PDF

Stirling-Tools · Documents

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What is Stirling PDF?

Stirling PDF replaces a pile of single-purpose online PDF sites and desktop licences with one web app on your own server. Staff can merge, split, compress, convert, OCR, sign and redact documents without uploading them to a third party, and developers can reach the same operations through an API.

Stirling PDF is a PDF toolbox you run in a browser from your own server. It merges, splits, compresses, converts, OCRs, signs and redacts documents, and exposes the same tools through a REST API. Files are processed on infrastructure you control.

Core capabilities

  • Merge, split, rotate, compress, watermark, sign and redact PDFs from a browser interface.
  • Run OCR and convert between PDF, Office files, HTML and images on your own server.
  • Call the same tools from your own systems through a REST API with built-in Swagger docs.

Dozens of PDF jobs in one place

The tool list covers page work such as merging, splitting, rotating, cropping and page numbers, plus compression, watermarks, stamps and form flattening. Security tools add passwords, permissions, certificate signing, timestamps and signature checks. Redact blacks out text or areas, Sanitize removes risky content, and OCR turns scans into searchable files. Convert handles Office files, HTML, images and PDF/A.

  • Merge and split
  • OCR
  • Redaction
  • Signing
  • Convert

Documents stay on your server

Because the app runs on your own machine or network, documents are processed there instead of on a public converter site. Every tool is also available as a REST endpoint, with Swagger documentation served by the app itself, so an internal system can compress, convert or OCR files automatically. On an install without login the API needs no key.

  • Privacy
  • REST API
  • Swagger
  • Automation

Self-hosting and licence: open core

Stirling PDF is open core. The repository is MIT licensed, but folders such as app/proprietary, app/saas, engine and parts of the frontend fall under the Stirling PDF User License, which requires a paid licence for production use. The default Docker image includes the proprietary login and admin layer. Its Free plan allows 5 users, and Team and Enterprise plans add seats and features. An MIT-only build, like the ultra-lite image, has no login, OCR or Office conversion. The default image runs with Docker, mounted data folders and about 4 GB of memory.

  • Open core
  • MIT
  • Docker
  • Paid plans

Where it fits

Use cases

  1. 01

    Assemble and shrink a document bundle

    Drop several PDFs into Merge, put them in order, then add page numbers and run Compress. You get one smaller file that is ready to email or upload to a portal.

  2. 02

    Redact a file before sharing it

    Open Redact and black out names, account numbers or whole areas of the page, then run Sanitize to strip embedded JavaScript and attachments. The cleaned copy can go to a client or auditor.

  3. 03

    Make scanned paperwork searchable

    Upload scanned invoices or contracts, run OCR in the language of the documents, then convert the result to PDF/A for long-term archiving. Extra OCR languages can be added to the mounted tessdata folder.