Here is one pretty good PDF protecting application released for all mac users by team Core.
Description: PDF Protector is an easy to use utility to encrypt or decrypt your
- Supports Adobe Standard 40-bit Encryption and Adobe Advanced 128-bit Encryption.
- Password protect opening of the document.
- Unlock protected documents with the correct password.
- Prevent printing of the document.
- Prevent copying and changes to the document.
- Easy to use.
- Compatible with all common PDF readers, such as Preview.app or Adobe Reader
- Does NOT need Adobe Acrobat software.