How to merge PDFs without uploading them
You can combine several PDFs into one entirely in your browser, so the files are never uploaded to a server, using a browser-local merge tool.
Steps
VERIFIED Open the merge tool, add your PDFs, put them in the order you want, then select Merge and review. The merged PDF is built on your device and opens for review. Download or share it when ready.
How to confirm nothing was uploaded
VERIFIED Open the Network tab before you merge, or go offline after the page loads; the merge still completes and no request carries your document.
Limits and honest caveats
VERIFIED Because the work runs on your device, very large files are bounded by your device memory. SumoPDF shows its current beta limits on the tool page. Password-protected PDFs are not supported; the tool says so rather than produce a broken result.
Questions
Are my PDFs uploaded when I merge?
VERIFIED No, for this browser-local tool.
Is there a watermark or account?
VERIFIED No.