In order to secure a PDF with a password when opened in Adobe Acrobat 9 Pro, press the secure button and go into password security settings. Here you can change on what versions of this software the file will run on, the next option asks which portion of the document is to be encrypted when a password is placed. Further below here is where you actually choose the password, this ensures that only people who know the password will be able to see the contents of the document. Below this is the document permissions password, this has many options that come with it. First off, printing can disabled or only printing in low resolutions can be enabled depending on if you know the password. Second is the option to determine what kind of changes can be made to the document by other users. Lastly is the option to allow users to copy text or pictures off the document. A password will take care of all these things.