Passwords for PDF documents are one way to protect your document. Security is a big topic but here we are only discussing passwords with PDF files. There are a few scenarios where you will decide to add a password to your PDF to protect it. Here are two scenarios found at the Adobe website:

• You want only certain people to view your PDF. The easiest solution is to add a password to the PDF and send it to your intended recipients.
• You don’t want anyone to print or edit your PDF. You can block printing and editing from the same dialog box that you use to add a password.

Passwords are useful if you are concerned about protecting your intellectual property (copyright) because they can prevent people from opening your document and copying and pasting the contents into their own document.

How to Add a Password

If you are using Acrobat Pro 9 then you find this functionality under Advanced -> Security -> 2 Encrypt with Password. If you are using Acrobat Pro DC then go to Tools -> Protect -> Encrypt -> Encrypt with Password.

A large dialog box opens. The first two check boxes are not mutually exclusive. You can check both, or just check one. The text in red is showing which options are available and adding further comments. The passwords for the two types of security (open and restrict) cannot be the same. You will need to re-enter your password(s) after clicking OK.