Opening PDF document with security restriction
When you receive a PDF document that is protected by security restrictions, you may need to type a password before you can open the document. When a document has restricted features, any tools and menu items related to those features will not be functional.
A PDF document can have two kinds of passwords: a Document Open password and a Permission password. If a document is set with a Document open password, you can open the document by typing in the password.
If the PDF document has both types of passwords, it can be opened with either password, but a user can make changes only with the Permissions password.
If you do not have the password you will need to contact the document author to ask for the password or used an unsecured version of the file.