TL;DR : Do you really need an Adobe subscription to merge or sign a PDF? No. Stirling-PDF is a complete toolbox that installs on your own server: merge, split, compress, convert, sign, recognize text (OCR), password-protect. More than 50 operations, right in the browser, with no Adobe subscription and without sending your documents to an unknown site. Free for one person or a team of five, paid beyond that. Its historical limit (rewriting a PDF's text) is starting to fall with version 2.0, but that feature stays reserved for the paid licence.
Merging two PDFs should take ten seconds. Instead, we upload a sometimes-confidential document to an unknown "free" site and cross our fingers. We've all done it at least once. Stirling-PDF exists precisely to kill that reflex.
What it actually does
Stirling-PDF gathers in one place the vast majority of everyday PDF manipulations: merge and split, rotate, compress a file too heavy for email, convert to and from images or office documents, add or remove a password, apply a signature, a watermark, or run text recognition (OCR) on a scanned document. In all, more than fifty tools, all reachable from a simple web page.
For office conversion (Word, Excel or images to PDF, and the other way around), Stirling-PDF relies on LibreOffice in the background. OCR runs on Tesseract, the open-source text-recognition engine, backed by OCRmyPDF to clean up scans (deskewing, noise removal).
The detail that changes everything: your documents don't leave
The real value isn't the feature list, it's where they run. Because Stirling-PDF runs on your own server, the employment contract, the invoice or the medical file you're handling never leaves your infrastructure. Files are processed and then deleted, without passing through a third party. For an SMB that handles personal information, that's the difference between good practice and a Law 25 compliance risk.
Adobe Acrobat vs Stirling-PDF
| Need | Adobe Acrobat Pro | Stirling-PDF |
|---|---|---|
| Merge, split, rotate | Yes | Yes |
| Compress, convert, OCR | Yes | Yes |
| Visual signature, watermark, password | Yes | Yes |
| Rewrite a PDF's text | Yes | Since v2.0, on the paid licence |
| Where your files live | Adobe servers (cloud) | Your server |
| Model | Per-seat subscription | Free up to 5 people, server licence beyond |
The installation and licence, in practice
The installation is light: one container, a reverse proxy, and the whole team can reach it from the browser. You can keep it on the internal network or publish it in a controlled way.
On the licensing side, Stirling-PDF moved to an "open-core" model in 2025: the core stays free (MIT licence) and free for individual use or a team of up to five. Beyond that, a server licence takes over, around US$99 per month or US$999 per year, for an unlimited number of users. It's a flat plan, not a per-seat price: a cost to weigh against the per-employee Adobe subscription you're replacing.
What's missing (and what just changed)
For a long time, the criticism aimed at every PDF tool fit in one sentence: you don't rewrite a PDF's text as freely as a Word document, because the format wasn't designed for it. Stirling-PDF started filling that gap with its version 2.0 (late 2025), which introduces real text editing. Two caveats, though: that feature is reserved for the paid licence, and the very nature of PDF still makes fine layout retouching tricky. For professional prepress, you stay in specialized tools.
Another limit to keep in mind: Stirling-PDF's signature is a visual signature (you place an image). For an electronic signature with legal, cryptographic and verifiable value, you need a different tool, like LibreSign. And OCR quality, as always, depends on the quality of the scanned document you started with.
Our take
For 90 % of an office's PDF needs (assembling, lightening, signing, protecting, recognizing text), Stirling-PDF advantageously replaces an Adobe subscription, with the major benefit that no document transits through a third-party server. We often deploy it alongside a free document management system : a formidable duo for ending pay-per-page.
Curious about replacing the Adobe subscription with a tool that's yours? Write to us and we'll look together at what fits your team.
Sources
- Stirling-PDF : official site
- Stirling-PDF on GitHub : list of features and documentation
- Open-core licensing model : free and server plans