PDF Password - PDF specification allows owners to specify up to two passwords for a document to protect and encrypt it: an owner password and a user password.

• Opening the document with the correct owner password (assuming it is not the same as the user password) allows full (owner) access to the document.
• Opening the document with the correct user password (or opening a document that does not have a user password) must follow the user access permissions(e.g. copy and print) specified in the document by its owner.

Doxillion Document Converter needs access permission for copy or extract page contents from the document according to PDF specification. Therefore, Doxillion requires to enter an owner password if the PDF document does not have "copy" permission, although PDF readers can open it. Doxillion does not pop up this dialog if the PDF is not encrypted or disabled "copy" permission.