Stirling PDF - Private, Open-Core PDF Editor with 60+ Tools and Self-Hosting

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Stirling PDF - Private, Open-Core PDF Editor with 60+ Tools and Self-Hosting

Stirling PDF — the open-core PDF platform you can run on your own machine or server

Stirling PDF is a private PDF editor and automation platform that runs in the browser, as a desktop app, or on your own server. It puts more than 60 PDF operations — editing existing text, merge, split, compress, convert, OCR, redact, sign, protect and compare — behind one workspace, and exposes the same operations through a REST API and an MCP server so scripts and AI agents can drive them. The project reports 30 million downloads, use by 55,000 companies and presence in 75% of the Fortune 500; the last two are vendor figures, not independent audits.

From a weekend experiment to an open-core company

Anthony Stirling released the first version in January 2023 as a 24-hour weekend experiment: one engineer, four tools, a Reddit post. The GitHub repository is now one of the most-starred developer tools on the platform — about 96,500 stars and 9,300 forks on 14 November 2026 — and the official Docker image has passed 18.5 million pulls.

In September 2024 the project moved to an open-core model with Open Core Ventures: the core tools stay open and free while enterprise features such as SSO, audit logging and automation are commercially licensed. Matt Joseph joined as CEO in March 2025 and Anthony Stirling became CTO. The V2 redesign shipped in September 2025, when the old stirlingpdf.com and stirlingpdf.io addresses began redirecting to stirling.com. The current release is v3.3.0 (5 November 2026), which upgrades the new Stirling Office Convert engine, adds Windows ARM64 support, improves mobile scanning and hardens request handling.

Four ways to run it

Mode	What it is	Best for
Cloud	A browser workspace at stirling.com with nothing to install. Free accounts get 1,000 monthly credits for automation and AI work.	Trying it, or working from a machine you do not control.
Desktop	Windows installer and macOS app, both free for individuals. The Linux build is a Java .jar you start manually. A Local Only mode keeps files on the machine without an account.	Offline editing and privacy-sensitive documents.
Server	Docker image, Kubernetes Helm chart or bare-metal JAR. The free self-hosted plan covers five users and includes all PDF tools, the REST API, OIDC single sign-on and server certificate signing.	Teams that want a private PDF service on their own infrastructure.
Enterprise	Air-gapped installation, offline licence activation, SAML2 SSO, SCIM provisioning, audit logs, data residency and uptime SLAs.	Regulated, government and large-organisation deployments.

What the 60+ tools cover

The tool picker groups operations by task rather than by product name. The quick-access row holds the eight most-used tools, each with a keyboard shortcut.

Group	Representative tools
Quick access	PDF Text Editor (edit existing text and images), Page Editor / PDF Multi Tool (rotate, reorder, delete, split, insert pages), Merge, Compare (text differences between two PDFs), Compress, Convert, OCR / Cleanup scans, Redact.
Signing	Draw, type or upload a signature; add a certificate-based digital signature that proves who signed and shows later changes; add an RFC 3161 timestamp; validate existing signatures.
Document security	Password protection, permissions, watermark, stamp, sanitize (remove JavaScript and embedded files), flatten, unlock form fields.
Page formatting	Crop, rotate, auto-rotate, split, reorganize, page size and scale, page numbers, multi-page layout, booklet imposition, single large page, attachments and PDF portfolios.
Extraction and removal	Extract pages or images, remove pages or blank pages, strip annotations or images, remove a known password, remove certificate signatures.
Content and forms	Add text or images anywhere, annotate and comment, fill forms, auto-detect form fields, edit metadata and the table of contents.
Advanced	Adjust colours and contrast, repair damaged files, detect and split scanned photos, overlay PDFs, replace or invert colours, inspect embedded JavaScript.
Automation	Save a chain of tools as a repeatable workflow, auto-rename files from their title, watch processing folders, call every operation from the API.

Conversion reaches beyond PDF: Office documents, HTML, Markdown, ebooks, images and PDF/A are all supported, and the new in-house Office Convert engine is taking over Office conversion while the project works to remove the old LibreOffice dependency. Office Convert is still in beta in v3.3.0. The interface is translated into more than 40 languages.

AI, automation and the developer surface

AI is built into the workspace rather than bolted on as a separate chatbot. Open the Stirling AI assistant, describe the change, and it runs the matching tool on the files you have open.

AI capability	What it does
Chat assistant	Runs tools on request, for example “merge these into one PDF” or “convert this to PDF”.
Document questions	Answers questions about a PDF's content, such as “what is the payment deadline?”.
Math auditor	Checks tables and totals for calculation errors.
PDF comment agent	Adds review comments to a document from an instruction.
Create PDF from prompt	Builds a new PDF from a written description.

The Processor extends this to batches: sources such as API calls, cloud storage, email attachments, watched folders and webhooks feed no-code pipelines, while policies classify, standardise, redact or route every arriving file and leave an audit record. Everything is callable from the REST and Pipeline APIs or through the MCP server, with connectors for SharePoint, Google Drive, Box, email and webhooks, plus a Telegram bot. Admins can enable AI on a self-hosted server, choose model providers, keep documents local with RAG, and turn individual capabilities off; on desktop, AI requires a Stirling Cloud sign-in or a connected server and is unavailable in Local Only mode.

Pricing at a glance

Plan	Price	Includes
Free	$0, no card	60+ PDF tools, web, desktop and self-hosted use, 1,000 monthly credits. A self-hosted Free server is limited to 5 users.
Team	$99/month	100 users included, SSO, team workspace and invites, extra capacity in blocks of 100 users, one bill instead of per-seat licences, central control of the tool catalog and editor deployment. External database, clustering, S3 storage, Prometheus metrics and custom metadata also unlock here.
Enterprise	Custom	Everything in Team plus air-gapped deployment, SCIM, data residency, audit logs, uptime SLAs and custom agreements.
Processor	1¢ per credit	Prepaid or metered PDF automation, with the first 500 runs free according to the pricing page.

The editor itself is free forever for individuals; the paid tiers are about administration, scale and compliance rather than unlocking the basic tools.

How it compares with the alternatives

Against Adobe Acrobat, Stirling's advantage is not a deeper prepress toolkit but a different ownership model: the core is open, the server can sit inside your network, and there is no mandatory subscription for ordinary editing. Against upload-first sites such as Smallpdf or iLovePDF, the difference is where the file goes — a self-hosted or desktop install never has to send a document to a third party. Against a full document suite such as ONLYOFFICE, Stirling is deliberately PDF-centric: it edits, secures, signs and automates PDFs extremely broadly, but it is not a replacement for a word processor or spreadsheet with native OOXML round-tripping. The closest fit is an organisation that already treats PDFs as a workflow input and wants the processing to happen on infrastructure it controls.

Honest limits

Open core, not a single permissive licence. The repository is MIT except for directories such as app/proprietary, app/saas, engine and the editor's cloud, desktop and processor folders, which carry a separate Stirling PDF User License. That licence restricts production use without a subscription, so read LICENSE before standardising on it commercially. The marketing claim that the source can be run “without asking us for anything” applies to the MIT-licensed core, not every directory.
The headline customer numbers are vendor claims. “55,000 companies” and “75% of the Fortune 500” come from Stirling's own pages. The About page still displays an older “21M downloads” figure while the homepage says 30M+, so treat the statistics as directional.
The free tier has real ceilings. A self-hosted Free server allows 5 users; external databases, clustering, S3 storage, Prometheus metrics, SAML, audit logs and offline activation move up to Team or Enterprise. Cloud AI and Processor runs consume credits.
AI is not fully local on desktop. Local Only mode omits the assistant. Using AI means signing in to Stirling Cloud or connecting to a server that has AI enabled, which changes the privacy model for the documents you ask about.
Conversion fidelity is the weak spot of every PDF suite. Office Convert is still beta in v3.3.0 and is being positioned to replace LibreOffice; heavily formatted Office files, unusual fonts and complex layouts can still shift. Keep the original application for documents where pixel-perfect round-tripping matters.
Linux desktop is not a packaged app. The download page offers Windows .exe and macOS .dmg, but Linux users are pointed at a manually started Java .jar. There is no native iOS or Android editor; the mobile scanner runs in the phone browser.
Some enterprise features are licence-gated by design. SSO, audit logging, air-gapped activation and advanced administration are paid rather than missing by accident. Small teams should price Team before assuming the free edition covers them.

Who it is for

Stirling PDF fits people and teams who handle PDFs often, care where the files are processed, and want one consistent set of tools across a browser, a desktop and a server. It is especially strong for IT and operations teams that already run Docker or Kubernetes, for regulated environments that cannot upload documents to a SaaS converter, and for developers who want PDF operations behind an API or an MCP tool rather than a desktop menu. It is a weaker fit for someone who mainly needs a full word processor, for pixel-perfect print production, or for a non-technical user who wants a single mobile app.

Stirling PDF is developed by Stirling PDF Inc., founded by Anthony Stirling with Open Core Ventures; Matt Joseph is CEO and Anthony Stirling is CTO. The GitHub organisation is based in the United Kingdom. The project is not affiliated with Adobe.

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