EncryptionUserPassword Property

The user password

This password protects the document against unauthorized opening and reading.

If a PDF document is protected by a user password, it cannot be opened without a password. The user or, if set, owner password must be provided to open and read the document.

If a document is not protected by a user password, it can be opened by without a password, even if an owner password is set.

If the password contains characters that are not in the Windows ANSI encoding (Windows Code Page 1252), the output document's compliance level is automatically upgraded to PDF version 1.7. This is because older PDF versions do not support Unicode passwords.