Stirling PDF: Over 50 Free PDF Tools, Like Adobe Acrobat Without the Subscription

Stirling PDF is a free open source PDF editing platform that puts over 50 PDF tools in one place, and it runs wherever you want it: as a desktop app, in the browser, or on your own server. It edits, signs, redacts, converts, and automates PDFs without sending your documents to an outside service, which is the whole reason it exists. It has 96,500 stars on GitHub, making it the most starred PDF application there, and its interface is available in more than 40 languages. The comparison it invites is Adobe Acrobat, and it is a fair one: Acrobat charges a monthly subscription for tools that most people use a few times a month, while Stirling PDF gives you the same everyday jobs, merging, splitting, compressing, signing, and converting, for free, in an app you can run yourself. Its core is free and open source, and some enterprise features and server plans are paid, which the project states openly.

The tool list covers the PDF jobs people actually do. Merge several PDFs into one, split one into pages or ranges, rotate and rearrange pages, add or remove them, and extract a single page. Sign documents, add watermarks and stamps, redact sensitive text, and flatten forms. Compress a bloated PDF before emailing it, convert PDFs to images and Office formats, and convert images and documents back into PDF. There are tools for adding page numbers, headers and footers, and for repairing damaged files. The dashboard groups everything by task, so you pick the job first and the tool second, which is the right order for software most people open only when a PDF is misbehaving. Every tool runs locally or on your own server, so the document never has to travel to a stranger's upload page, and that alone is worth switching for anyone who handles contracts, medical forms, or anything with a signature on it.

One of the most useful tools is OCR, which pulls text out of scanned pages and turns a flat image of a document into selectable, searchable text. That is where the real work starts, because OCR output is rarely clean on the first pass: stray characters, broken line wraps, and headers mixed into the body. An AI Text Cleaner is the natural next step, stripping the filler and formatting junk out of the extracted text so it reads like a document again. If you have two versions of the same document, for example before and after a redaction, or a draft and a signed copy, a Text Diff shows exactly what changed between them, line by line. And when you need to know how long the extracted text actually is, a Word Counter counts the words in seconds. The point is that Stirling PDF does not stop at extraction: it hands you text you can actually work with, and the tools around it finish the job.

Stirling PDF was built for people who do not want their documents on someone else's server, and the architecture shows it. Run it as a personal desktop app, open it in your browser, or deploy it on your own servers with a private API, and in every case your files stay where you put them. That matters more than it sounds. The usual way to merge two PDFs online is to upload them to a free tool, wait, and download the result, which means a copy of your document sits on a server you do not control, under a privacy policy you did not read. Stirling PDF removes that trade entirely: the processing happens on your machine or your server, and nothing is sent anywhere unless you choose to send it. For teams handling HR paperwork, legal documents, or anything under a retention policy, self-hosting turns a convenience tool into a compliant one, and the private API means your own systems can call it without routing documents through a third party.

Beyond the one-off tools, Stirling PDF is built for repeat work. No-code pipelines in the UI let you chain tools together, so a folder of incoming PDFs can be compressed, watermarked, OCRed, and renamed by one workflow instead of by hand. Nearly every tool has a REST API, so developers can plug PDF processing into their own systems: generate a report, stamp it, and archive it without a human clicking anything. The project says the API can process millions of PDFs, and the enterprise side adds single sign-on, auditing, and flexible on-premises deployments for organizations that need to prove who did what to which document. That is a different class of feature from a free merge tool, and it is why Stirling PDF shows up in offices as well as on home desktops: the same app that fixes one PDF for a student also runs the document pipeline for a company.

Getting started takes one command. With Docker installed, run docker run -p 8080:8080 docker.stirlingpdf.com/stirlingtools/stirling-pdf, then open localhost:8080 in your browser and the full dashboard is there. There is also a desktop client for people who want an app icon instead of a terminal, and Kubernetes manifests for teams deploying it at scale. The full installation guide covers desktop, server, and Kubernetes options, and the API documentation lists every endpoint. Development uses Task as its command runner, with task dev for a local run, and the project welcomes contributions with a published guide. The interface speaks more than 40 languages, the community hangs out on Discord, and bug reports go through GitHub Issues. For a tool that does this much, the install is unusually small: one Docker command, one browser tab, and you are editing PDFs.

Stirling PDF is open-core, and it is worth saying exactly what that means. The main application is free and open source under the MIT license, and you can run it, self-host it, and use its core tools without paying anything. Some enterprise parts are paid: server plans, single sign-on, auditing, and certain proprietary components that live in separate directories under their own licenses. The README and the license file both say this in plain language, and the paid offerings page lists what costs money. That is an honest model for a project of this size: the everyday tools stay free, and the organizations that need compliance features pay for them. If you only need to merge, split, sign, compress, or OCR a PDF, you will never see a paywall. If you run it for a company with SSO and audit requirements, that is what the paid plans are for.