I don't know what kind of security you have, editing restriction or open restriction. For the latter one, it probably hard to unlock the file and I assume your protection is the former type. If you want to edit it I suggest you to convert pdf to editable word with a pdf converter, usually it can automatically remove this kind of password and transform it to word document for editing case. Remember pdf is not designed as an import format so even if you unlock it, you still need to make it editable. http://www.pdfeditor.org/