What Lock PDF does
Lock PDF rewrites one verified document with Ghostscript PDF 1.7 output and 128-bit revision-3 compatibility encryption. The entered password is applied as the user password, with a derived owner-password value used by the conversion command.
This compatibility mode is intended for broad PDF-reader support, not modern high-assurance encryption. The tool does not recover forgotten passwords, and the rewritten file may not preserve advanced structures or existing digital signatures exactly.
How to use Lock PDF
- Choose one verified PDF up to 25 MB that you are authorized to protect.
- Enter and confirm a new password of 4–48 printable ASCII characters with no surrounding spaces.
- Protect the PDF, download the result, and test the password in a separate reader before deleting any backup.
Important details
Protection uses a compatibility mode
Ghostscript writes a PDF 1.7 document with revision-3, 128-bit encryption. This is weaker than current AES-based protection and should not be described as unbreakable or suitable for highly sensitive secrets.
The document is rewritten
Ghostscript interprets and emits a new PDF rather than modifying a few bytes in place. Forms, metadata, color, complex objects, and signatures can change, so compare the output with the original.
Practical uses
- Add basic opening-password protection before sending a routine document.
- Create a compatibility-protected copy for readers that support older PDF encryption.
- Separate a protected distribution copy from an archived unprotected original.
Privacy and limitations
The PDF and password are sent to PagesTools only for this conversion request. Temporary input and output files are removed when the response completes, fails, or is cancelled; the password is not stored by the tool.
Uploads are limited to 25 MB, generated PDFs to 50 MB, and processing to 55 seconds. Passwords must contain 4–48 printable ASCII characters. Detectably active or invalid PDFs are rejected, and 128-bit compatibility encryption is not modern high-strength protection.