From Mapsoft Computer:
Acrobat has various in-built security features controlling access to PDF documents. Within Acrobat these features have to be set on a file-by-file basis (by selecting the File > Save As menu item). Mapsoft SecuritySetter allows you to set these security features. Using the SecuritySetter tool you can set two types of password to limit access to your PDF files. Passwords can be changed or deleted. Tryout is stamped on your PDF document.