Stirling PDF is an open-core PDF toolkit from Stirling PDF Inc. Its desktop app brings more than 60 operations together, including merging, splitting, reordering, rotating, compressing, signing, redacting, and adding watermarks, page numbers, or passwords. That breadth makes it useful for routine document work, while the distinction between local and connected tools matters when choosing how to process a file.
For daily use, Stirling PDF can handle common tasks without an account: select Local Only mode and documents are processed on your computer rather than uploaded. This is a practical fit for people who regularly rearrange pages, reduce file size, or remove sensitive information, though the offline engine does not cover every tool in the app.
Working locally or connecting to a service
On first launch, users can sign in to Stirling Cloud, connect to a self-hosted Stirling server, or continue without signing in. Local Only mode keeps processing on the computer, and tools that the built-in engine cannot run are marked with a cloud badge. OCR, Office-to-PDF conversion, and PDF-to-Word conversion require Stirling Cloud or a self-hosted server, so users who need those functions fully offline will need to operate their own server.
Cloud and server connections expand the available processing options, but they change where some work is performed. In Stirling Cloud, files for tools that the local engine cannot handle are sent to the cloud. Pipelines can chain multiple operations into automated workflows, while AI tools and folder processing also use cloud credits; these connected features are separate from straightforward local editing.
Tools for document changes and protection
The toolkit covers both page-level organization and changes to document content. Users can combine or separate PDFs, change page order or orientation, compress files, and add visual elements such as watermarks and page numbers. For sensitive documents, it can apply signatures, redact text or areas, and protect files with passwords. These operations make the app relevant to both preparing documents for sharing and applying basic safeguards before distribution.
Stirling PDF is available on Windows 10, Windows 11, macOS 10.15 or later, Linux, the web, and self-hosted servers. On Windows, installation uses an MSI for all users and requires administrator rights. The Windows app also requires the Microsoft Edge WebView2 Runtime; if the app does not open after installation, that runtime may need to be installed.
License and practical fit
The license is open core: the core is MIT, while the desktop app and paid features are proprietary. The Free plan is available to individuals at no cost, requires no payment card, and includes 1,000 monthly credits for automation. Team plans add SSO and administration. Because automation credits apply to pipelines, the free local workflow and credit-using cloud functions should be considered separately when planning regular use.
Overall, the strongest case for Stirling PDF is its combination of numerous everyday operations with a local mode that does not require an account. The main qualification is that OCR and several conversion tasks are not available through the desktop app’s local engine alone. It therefore suits users whose regular work is mainly merging, splitting, compressing, signing, or redacting, while workflows dependent on offline OCR or PDF-to-Word conversion require a self-hosted server.