Refusing to send your PDFs to a consumer cloud is a healthy reflex — and two projects answer it seriously. Stirling PDF is the open-source reference in the space (over 90,000 GitHub stars); Document Flare plays on the same privacy field with a radically different architecture. This comparison says what each does well — including what Stirling does that Document Flare does not.
One promise, two architectures
Both tools share the same promise: your documents never end up on a third party’s server. But they implement it in opposite ways.
- Stirling PDF brings processing to you, on a server you host: Docker, Kubernetes or a standalone JAR. Privacy comes from the fact that the infrastructure is yours — provided you deploy it, secure it and maintain it.
- Document Flare removes the server from the equation: processing runs inside your browser, in JavaScript/WebAssembly. Your machine is the “server”. There is nothing to host because there is nothing to serve.
So the difference is not the level of privacy — both offer it — but who does the infrastructure work: your ops team, or no one.
Synology DS223j — 2-bay NASTwo-bay NAS with remote access: your personal archive off the cloud.affiliate
Installation and maintenance: the real cost of self-hosting
Self-hosting Stirling PDF is not trivial. According to its documentation, a production deployment involves a docker-compose, a reverse proxy with HTTPS, updates to track, backups, exposure hardening — in short, sysadmin skills and recurring time. On licensing, Stirling’s documentation states that free self-hosting covers up to 5 users in a business context; beyond that, a Team plan ($99/month, 100 users, SSO, external database) or Enterprise plan (SAML, air-gapped deployment, SLAs) is required.
To be fair: Stirling also offers a native desktop app (Windows, macOS, Linux) that processes files locally with no account. It narrows the gap — but it remains software to download, install and update on every machine.
Document Flare has nothing to install: open the URL, drop the file. The app is installable as a PWA for those who want an icon — with direct Android sharing and .pdf opening from the system — but nothing requires it. No account, no server to patch, no license to manage.
The comparison table
| Criterion | Stirling PDF (self-hosted) | Document Flare |
|---|---|---|
| Where files go | Your server | Nowhere: processed in the browser |
| Installation | Docker / Kubernetes / JAR (or desktop app) | None — a URL, optional PWA |
| Maintenance | Updates, HTTPS, backups, server security | None |
| Skills required | System administration | None |
| Multi-user, SSO | Yes (paid plans beyond 5 users) | No — single-user tool |
| Automation | API, webhooks, pipelines | No |
| Large files | Limited by your server | 50 MB / 1,000 pages per file |
| Verifiable privacy | You control the infrastructure — securing it is on you | Network tab: no request carries the document |
What Stirling PDF does that Document Flare does not
An honest comparison has to say this. Once the server is up, Stirling PDF offers things a browser cannot match:
- a full OCR pipeline (OCRmyPDF) producing a PDF with a text layer — Document Flare’s OCR outputs a plain text file, not a searchable PDF;
- an API and automation pipelines to process documents continuously;
- multi-user support: SSO, team management, audit logs;
- rich office-format conversions executed server-side (Document Flare does not expose Office conversions in its public version);
- heavy files: the limit is your RAM and disk, not 50 MB.
What Document Flare brings to the table
Conversely, the browser model has advantages of its own:
- Zero install, zero account — including on a machine where you have no rights to install software or run Docker;
- demonstrable privacy: not a policy to believe, but a Network tab to open — the protocol is in our local processing guide;
- tools self-hosting does not really provide: personal-data detection (IBAN, social security numbers, cards, emails…) and destructive redaction by page rasterization, described in our article on the science of redaction;
- zero marginal cost: no VPS, no admin hours, no plan beyond 5 users.
Which one should you choose?
The two tools are complementary, not rivals:
- Team, existing infrastructure, automation, SSO, large volumes: Stirling PDF is the right tool — self-hosting has a cost, but it buys exactly those capabilities.
- Immediate individual need, locked-down workstation, a document too sensitive to touch even your own server: Document Flare removes infrastructure from the equation.
One important nuance: the hosted version of Stirling at stirling.com runs on credits and processes files in their cloud — the “your files stay with you” promise only holds for the desktop and self-hosted modes. To dig into the all-local model, see our pillar on PDF tools without upload and our comparison of local alternatives to iLovePDF.
The right hardware
Synology DS223j — 2-bay NASTwo-bay NAS with remote access: your personal archive off the cloud.affiliate
Seagate Expansion — 2 TB external HDDTwo terabytes on a budget: mass archiving without a subscription.affiliate
