Rohman
Search "open source PDF editor" and you get a wall of listicles that mash together three completely different things: free software, software with public source, and software that does not phone home. Same query, three answers. Pick the wrong one and you end up installing Docker to open a tax form.
This is the survey I wish existed before I went down that hole.
One query, three intents
People typing "open source PDF editor" usually want one of these:
- Free as in beer. "I refuse to pay Adobe $20 a month." Source code visibility is irrelevant. They want gratis.
- Free as in freedom. Auditable code, no telemetry, modifiable, redistributable. License matters. GPL, AGPL, MIT.
- Self-hosted or offline. "My documents do not leave my machine." This is about data flow, not source visibility.
These overlap, but they are not the same thing. Master PDF Editor 4 was free-as-in-beer on Linux and proprietary. Stirling-PDF is real FOSS, but if you point your browser at a friend's hosted instance, your PDFs travel through their server. Worth keeping straight before you commit to an installer.
Stirling-PDF, the heavyweight
Stirling-PDF is the closest thing the FOSS world has to an Acrobat replacement. About 78,000 GitHub stars as of April 2026. Java/Spring backend, TypeScript frontend. Roughly 50 tools covering edit, merge, split, OCR, redact, sign, convert.
It runs as a desktop app, a self-hosted server, or a Docker container. Most people meet it through Docker, which is the wall. If you already run a homelab, Stirling-PDF is fantastic. If you don't, "install Docker" is a non-trivial day for someone who wanted to fix a typo on a lease.
One more thing worth flagging. The project shifted to an open-core model. Some enterprise features sit behind a commercial license. The base toolkit is still MIT, but "fully FOSS" needs that caveat now.
PDFsam Basic, the page-level utility
PDFsam Basic has been open source since 2006. AGPL-3.0, written in Java. Honest about what it does: split, merge, mix, rotate, extract. That is the whole list. No text edits, no image insertion, no annotation.
Two things to know. The free Basic version pushes upgrade prompts toward the paid Enhanced and Visual editions. And calling it a "PDF editor" is a stretch. It's a page-level utility. Use it for splitting and merging. Pair it with something else when you need to touch content.
LibreOffice Draw, the surprising part-time editor
LibreOffice Draw can open a PDF and let you edit it. In theory. In practice, missing fonts get rendered as boxes or substituted poorly, line wrapping breaks, text drifts past margins on export. The upstream bug report has been open long enough to qualify as a feature.
It's fine for filling forms or fixing a typo on a PDF you generated yourself, where the fonts are predictable. Painful for editing PDFs from third parties, which is the case most people actually have.
Inkscape, Xournal++, Okular: purpose-built tools
Inkscape treats a PDF page as a vector canvas. It imports one page at a time. A multi-page extension exists, and it is unreliable. The Poppler/Cairo importer turns text into uneditable paths. Useful for touching up a logo or a single-page diagram. Not a document editor.
Xournal++ is built for handwritten annotation. You import a PDF as a notebook background and write on top with a stylus. Highlights, shapes, text boxes, stamps. Markup, not modification. Erase your annotation and the underlying PDF is unchanged. Excellent at what it does, which isn't what most people mean by "edit."
Okular is the KDE viewer. It supports native PDF annotations and digital signatures. Cross-platform on Linux, macOS, Windows. Also a viewer, not a content editor.
Master PDF Editor, the asterisk
Master PDF Editor v4 was free for non-commercial use on Linux. Full editing, no watermark. Then v5 turned proprietary. Editing text, inserting images, and other tools watermark the output until you buy a license. It still gets recommended in old listicles. The rules changed.
What is actually missing
Most open source PDF tools are split-purpose. Stirling-PDF gets closest to a unified suite, and the typical install path is Docker. LibreOffice Draw is the only zero-friction option for non-form text edits, and its font handling is a known problem. Annotators don't change the underlying document. PDFsam doesn't touch content. Inkscape does one page at a time.
So if you want one tool that edits text, manages pages, fills forms, redacts, OCRs, and runs without a server you administer, there isn't a clean FOSS answer. That's the gap.
Open source is not the same as private
This part deserves bluntness. Open source does not mean private if you don't control where it runs.
- Stirling-PDF on your laptop via Docker → private. Files stay on the machine.
- Stirling-PDF on a $5 VPS → your PDFs traverse and live on someone else's hardware. Code is auditable. Storage is not private.
- A "free PDF editor" web app whose source you have never read → you're trusting both the code and the operator.
If your concern is "my data should not leave my device," self-hosting on the device itself is the only configuration that delivers it.
Where browser-local fits
Honest disclosure first. OxygenPDF is not open source. The source isn't published. On the freedom axis, that's a fail.
On the data never leaves your machine axis, it qualifies. Files are read into browser memory, processed by WebAssembly inside the tab, never reach a server. No upload, no account. Verify it yourself. Open the browser's Network tab while you use /tools/edit-pdf and watch it stay empty.
If your priority is auditable code, install Stirling-PDF. If your priority is "don't make me install Docker, just don't upload my PDF," browser-local is a closer match. Different answers for different definitions of the same word.
Side-by-side
| Tool | What it edits | Install | Self-host? | License | Curve |
|---|---|---|---|---|---|
| Stirling-PDF | Edit, merge, split, OCR, redact, sign, convert | Docker / desktop / server | Yes for web UI | Open-core (MIT + commercial) | Medium |
| PDFsam Basic | Split, merge, mix, rotate, extract | Native installer | No | AGPL-3.0 | Low |
| LibreOffice Draw | Limited text edit, page edit | Native installer | No | MPL-2.0 | Medium (fonts) |
| Inkscape | Vector edits, single page | Native installer | No | GPL-2.0+ | Steep for PDF |
| Xournal++ | Annotation only | Native installer | No | GPL-3.0 | Low |
| Okular | View + annotate | Native installer | No | GPL-2.0+ | Low |
| OxygenPDF | Edit, merge, split, OCR, redact, convert | None (browser) | No | Proprietary, browser-local | Low |
Pick by intent, not by buzzword
The honest answer to "what is the best open source PDF editor?" depends entirely on which of those intents you actually have.
Want auditable code and you run a homelab? Install Stirling-PDF. The 50-tool toolkit is real and the project is active.
Want a unified tool that doesn't upload your file and doesn't require Docker? Try OxygenPDF in your browser is closer to that, with the honest caveat that the source isn't public.
Want to merge a PDF and stop thinking about it? Neither label matters. Use whatever's in front of you and works.
The label is a proxy for what you actually care about. Skip the proxy.
