Stirling-PDF is an open source PDF toolkit you can self-host — split, merge, convert, OCR, compress, sign, and edit PDFs from one browser app, a private Adobe Acrobat and iLovePDF alternative that keeps your documents on your own server.

What is Stirling-PDF?

Stirling-PDF is an open source PDF toolkit that runs as a web app on your own server, giving you 50+ tools to split, merge, convert, OCR, compress, sign, watermark, and redact PDFs from one browser interface. It’s stateless by design — files are processed in memory and discarded after the operation, so nothing you upload leaves your infrastructure.

What is Stirling-PDF best for?

Stirling-PDF is for anyone who does routine PDF work and doesn’t want to upload sensitive documents to a free web converter or pay for a desktop suite. It suits privacy-conscious individuals, IT teams, and regulated organizations who want a single self-hosted toolkit for the everyday PDF jobs that would otherwise be scattered across a dozen sketchy online tools.

What can Stirling-PDF do?

Merge, split, rotate, crop, and reorganize pages
Convert PDFs to and from images, Word, and other formats (via LibreOffice)
Run OCR on scanned documents to make them searchable (via Tesseract)
Compress files, add or remove passwords, watermark, and redact content
Fill forms, add digital signatures, and flatten PDFs
Chain operations into no-code pipelines and drive everything through a REST API
Localized in 40+ languages, with no login required by default

Where does Stirling-PDF fall short?

OCR and format conversion lean on Tesseract, Ghostscript, and LibreOffice, which are CPU- and memory-hungry. The default 512MB Java heap can hit out-of-memory errors on large files, and OCR on a long scanned document can take minutes — with accuracy that trails Adobe’s commercial engine.
It’s a PDF toolkit, not a document archive. It processes files on demand but doesn’t store, tag, or index them like a document management system such as Paperless-ngx, so it won’t replace a searchable library of your records.
It’s open-core: single sign-on, team management, and full API/webhook automation pipelines sit behind the paid Server and Enterprise plans. The free edition is the tool catalog itself, with any authentication you configure yourself.

Is Stirling-PDF free?

Yes — the core Stirling-PDF is free and open source under the MIT license, and self-hosting costs only your own server. Paid tiers layer on convenience and team features: a hosted Stirling Cloud, a Server/Pro plan at $99/month (100 users, SSO, shared workspaces), and a credit-based Processor/Enterprise plan for API pipelines, SCIM, and air-gapped deployment.

What does Stirling-PDF replace?

Stirling-PDF stands in for Adobe Acrobat and web-based tools like iLovePDF and Smallpdf. It covers the same merge, split, convert, OCR, and sign jobs, but runs on hardware you control — so private documents never get uploaded to someone else’s cloud, and there’s no subscription.

FAQ

Is Stirling-PDF open source? Yes. The core application is MIT licensed and its code is public on GitHub. It follows an open-core model, so some enterprise features (SSO, audit logging, automation pipelines) are proprietary paid add-ons, but the toolkit itself is genuinely open source and free.

Can I self-host Stirling-PDF for free? Yes. Run it with a single Docker command on port 8080 and you get the full 50+ tool catalog at no cost — you only pay for the server. It boots straight into the UI with no login required.

Is Stirling-PDF a good Adobe Acrobat alternative? For everyday PDF tasks — merging, converting, compressing, signing, redacting — yes, and it keeps files private. If you need Acrobat’s polished editing UI or its higher-accuracy OCR on messy scans, the commercial product still has an edge.

What do I need to run Stirling-PDF? A machine with Docker and enough RAM for the work you do — 512MB is fine for light jobs, but OCR and Office conversions want extra CPU and memory. Tune the Java heap up for large files.