Stirling-PDF

What is Stirling-PDF?

Stirling-PDF is a locally hosted web application that handles dozens of PDF operations including merging, splitting, compressing, converting, OCR and signing. Because it runs on your own machine, sensitive documents never get uploaded to a third-party service.

Best for

Anyone who handles PDFs with personal or confidential content

Why choose Stirling-PDF

Stirling PDF is the rare utility that replaces a whole category of subscriptions at once. Merging, splitting, compressing, watermarking, converting, OCR, redaction, form filling and signing — the tasks people otherwise pay Adobe or a series of one-off web tools to do — all run locally. The privacy angle is the real argument: your contracts, medical records and ID scans never upload anywhere, which is not true of the free online PDF sites most people use.

Replaces

• Adobe Acrobat
• Smallpdf
• iLovePDF

Key features

• Merge, split, compress and rotate
• OCR and format conversion
• Password protection and signing
• Batch processing

What to watch out for

Be aware of the licence situation. Stirling PDF is open source but its main distribution is under a licence that restricts removing or rebranding certain enterprise features, which has caused friction in parts of the community; check the current terms if you plan to redistribute or resell. Functionally, OCR quality depends on the language packs you install and will not match commercial tools on poor scans. Very large PDFs, especially scanned documents of a hundred pages or more, can be slow and memory-hungry on modest hardware.

How to deploy

• Docker

Getting started

Docker is the intended deployment and the image is large because it bundles the conversion toolchain — give the container a few gigabytes of memory, or conversions will fail with unhelpful errors. Enable the login option even on a private network, since the tool can read any file you hand it. Set up the OCR language packages you actually need rather than installing every language. It pairs especially well with a document scanner workflow: dump scans into a watched folder, automate OCR and compression, and the whole pipeline stays on your own machine.

Typical setup

It runs as a single container on a home server or VPS, reached through a browser, with enough memory allocated for the bundled conversion toolchain. The workflow that makes it genuinely useful is scanner-driven: a watched folder collects scans, and OCR and compression run on everything that lands there, so documents are searchable without ever being uploaded. People who handle contracts, IDs or medical records pair it with an internal-only network location rather than exposing it publicly.

Who should look elsewhere

Do not plan to redistribute or rebrand it without reading the licence carefully, since parts of the project carry restrictions beyond a standard open-source grant. It is also a mismatch for anyone processing very large scanned documents on modest hardware, where conversions get slow and memory-hungry, and for high-accuracy OCR of poor-quality scans, which commercial tools still handle better.

Project health

• GitHub stars: 93,337
• Last code push: 2026-09-30
• Open issues: 588
• Status: actively developed

Figures pulled from the GitHub API and refreshed periodically.