Most free PDF tools upload your files to a server. Contracts, invoices, medical records — sitting on a stranger's machine for up to 30 days. FoldPDF does it differently. Everything runs in your browser using pdf-lib. Your files never leave your device — not even for a millisecond. No account, no uploads, no tracking. Works offline once the page loads. Free forever for core use. $5 one-time for unlimited files + drag-and-drop page reordering.