PDF editing on the desktop or on your own server
Stirling PDF puts everyday PDF work behind one web interface: merging, splitting, compressing, OCR, signing, redaction, and conversion to and from office formats. It ships as a desktop app for Windows, macOS and Linux, or as a server with a private API that runs in Docker, on Kubernetes or as a plain JAR. On a self-hosted server every tool runs on that server, so documents do not pass through an online PDF service. The company behind it, Stirling PDF Inc., also sells a cloud service and paid plans.
Certificate signing and a REST API for nearly every tool
- Certificate signatures identify the signer and expose any later edit. RFC 3161 timestamps and a validator for incoming signatures sit next to them.
- Permanent redaction of text, areas or whole pages, and a
Sanitizetool that strips JavaScript and embedded files before a PDF goes out. - REST endpoints for almost every tool, plus an MCP server through which agents such as Claude or GPT can call them.
- Stirling Processor runs a chain of tools on files from a folder, a storage service or a webhook, as a one-off batch or each time a file arrives.
- OAuth2 / OIDC single sign-on on the free plan since v3.0, and a UI available in more than 40 languages.
Free plan limits: five accounts, 1,000 automation units a month
Eight directories of the repository sit outside the MIT license. The README is titled "The Open-Source PDF Platform" and only says "open-core" in its last line. The LICENSE file lists them, including app/proprietary/, which holds authentication and accounts, auditing, automation and the MCP server among other code, and engine/, the AI engine. They fall under the Stirling PDF User License, which limits production use to subscribers and, without a subscription, allows only trial, evaluation or minimal use, never in a commercial or client-facing setting.
A server without a paid license stops at five users. The plans table gives the Free plan every PDF tool, the API and OAuth2 / OIDC sign-on. Team, at 100 users, adds an external database, clustering, S3 storage and Prometheus metrics. SAML2 sign-on and audit logging require Enterprise, though the README lists "SSO, auditing" without naming a plan.
Automation and API calls draw on a monthly allowance. A server not linked to Stirling Cloud gets 1,000 units a month, and a file costs one unit per 25 pages or per 5 MB, whichever is higher, per the processing allowance page. Processor pipelines, MCP calls, AI tools and API-key calls all count, and they stop until the next month once the units run out. Tools used by hand never count, and a Team license key makes API calls free.
The desktop app does not keep everything local. In Local Only mode nothing is uploaded, but OCR and Office, HTML or ebook conversions need Stirling Cloud or a server, according to the page on where tools run. In Stirling Cloud mode those tools are sent to the company's cloud.
The standard Docker image calls for 4 GB of memory. The Docker install guide suggests that figure for latest, which bundles LibreOffice, Tesseract, OCRmyPDF, Ghostscript and ImageMagick. latest-fat adds the AI engine, off by default, and goes up to 6 GB. latest-ultra-lite fits in 2 GB but has no OCR, no office conversions and no login, which rules out any paid plan.
Releases have come out almost weekly since v3.0.0. That release, published on 24 September 2026, brought the Processor, free OAuth sign-on and the automation allowance. Six more followed within a month, up to v3.2.2 on 24 October 2026.