In Acrobat if the PDF is set owner password, it can't be modified, I can't find any functionality to unlock.
Definition: A PDF owner password is the password used to set document restrictions in PDF files. In Adobe Acrobat, the PDF owner password is called the change permissions password.
As of the latest PDF version, document restrictions can include printing, changing the document, document assembly, content copying, content copying for accessibility, page extraction, commenting, filling of form fields, signing, and creation of template pages.
PDF owner passwords are easily removed with freely available PDF password removal tools, allowing full access to previously restricted PDF files.
A PDF owner password does not restrict the opening of a PDF file, only what can be done once opened. PDF user passwords are used to provide "document open" security in PDF files.
Also Known As: PDF change permissions password, PDF permissions password, PDF master password