Your files stay on your device
File processing runs in your browser. Documents are not uploaded to our servers. The site may download processing engines and send usage or feedback events without file contents.
How we handle your dataLaboratory · On your device
Protect PDF
Add an opening password to a PDF on your device. Files stay in your browser.
Engine:QPDF
The next tool opens in a new tab. Keep this tab open until the file arrives. The PDF is passed locally; it is not uploaded or saved in browser storage.
Was this tool useful?
Try an example
Download sampleThe downloaded PDF should require your chosen password and retain both pages.
What to expect
Protection uses AES-256 and sets a password to open the PDF; after opening, printing, copying and editing are not restricted. Unlocking requires the existing password; this tool does not guess passwords. Changing a PDF can invalidate digital signatures.
Processing stops after 30 seconds. Protected input can be up to 30 MB; output is limited to 30 MB.
The first run may download converter files and take a moment. If it fails, check your connection or try a smaller file. Cancel stops active processing; you can choose another file and retry.