PDF files are used in a wide range of applications that include everything from user's manuals to presentations. The ability to protect the information contained within a PDF document is one of the reasons many companies use PDFs as their preferred method of information sharing. The basic security options included with Adobe Acrobat allow you to set limitations on the reader's ability to open, print, or copy the information contained in a PDF.
Open the PDF file you wish to protect.
Click on the "Secure" icon to open the drop-down menu.
Click "Password Encrypt" and choose "Yes" if a confirmation box appears.
Click the check box next to "Restrict editing and printing of the document" under the "Permissions" heading.
Enter the desired password, and choose "None" from the drop-down menus of the "Printing Allowed" and "Changes Allowed" options.
Uncheck the box next to "Enable copying of text, images, and other content," and then press "OK."
Press "File" and "Save" to save the edited PDF. Close the document. The next time someone opens the PDF and tries to print or copy it, he will be prompted for the password.
Adobe Acrobat is a paid program and is not to be confused with the free Adobe Reader, which simply allows PDF files to be read.