Stirling-PDF

Everything the online PDF converters do, without uploading the document to anyone.

What it does

Stirling-PDF is a large collection of PDF operations behind one interface: merge, split, rotate, reorder and delete pages; convert to and from images, Office formats and HTML; compress; OCR with Tesseract; add or remove passwords and permissions; redact; sign; repair damaged files; compare two documents.

Its reason to exist is the alternative. “Free online PDF merge” means uploading the document to a stranger’s server, which is unacceptable for anything with an address, a signature or a bank detail on it. This runs locally.

Three ways to run it

The project started as a container and grew a desktop app, so there are now three deployments of the same tool. They differ in where the work happens, not in what it can do.

Route	What it is	When
Desktop app	A signed universal macOS `.dmg` that bundles the server and runs it locally	One Mac, nothing to maintain
Container	`stirlingtools/s-pdf`, reachable from every device on the network	A homelab, or a family that keeps asking you to merge PDFs
Hosted	Stirling’s own instance	Never, for anything you would not email to a stranger

The standalone download is the newer of the two local options and needs no Docker, no Java and no configuration — install it and it is an ordinary Mac application, with the same operation set as the container.

Notes

OCR language packs are downloaded separately and are worth adding for any non-English documents.
The container is the better choice the moment more than one device needs it: put it behind Tailscale rather than on the open internet.

Alternative to

Alternative	Type	Trade-off
Adobe Acrobat Pro	Subscription	The commercial standard, subscription
PDF Expert	Paid	Native, covers editing and OCR
Preview	Built in	Handles merging and page reordering
qpdf, Ghostscript and OCRmyPDF	Open source	The same operations as composable CLI tools
Smallpdf or Sejda	Freemium	The web services this exists to avoid uploading to