Stirling PDF
A self-hostable toolkit for merging, splitting, converting, compressing and signing PDFs.
Cost
Completely free
Fully free and open source.
Open source
Yes
The code is public. Anyone can inspect it, and it cannot be taken away from you.
Your data
Stays on your computer
Nothing is uploaded. This matters for anything confidential.
Use it for this
Doing PDF work without uploading the document to a stranger's website. This is the honest answer to 'free PDF converter'.
Do not use it for this
People who cannot run anything themselves — though a hosted demo exists.
A moment where you would reach for it
Merging and compressing a contract without uploading it to an unknown service.
How hard is it to pick up?
Straightforward, but expect an hour of figuring it out.
Worth knowing before you use it
Self-hosted, so files never leave your control. Most free online PDF tools cannot say that.
Other things that do this job
No tool is best at everything. These solve a similar problem, with different trade-offs.
About this entry
Checked on 1 Sept 2026. Prices and free limits change without warning, and often quietly. Treat everything above as a starting point and confirm on the official site before you rely on it.
Nothing here is sponsored. A tool appears because it solves a real problem, not because someone paid for it to be listed.