You may need to send someone a PDF containing sensitive information, such as your tax information, financial details, Social Security number, or other data. Obviously, you don’t want that information to end up in the wrong hands. If you password-protect your document, only the person who knows the password can open it.

Encrypting a Word Document may be the best option for collaborating with others, but sending important documents requires a PDF. There are, however, some complications here. Not only will you need to figure out a secure way to share the password, but Adobe Reader’s free version does not support password protection.

Password Security Basics

Passwords and restrictions on certain features, such as printing and editing, can be used to restrict access to a PDF. You cannot, however, prevent a PDF from being copied. The copies are subject to the same limitations as the original PDF. There are two kinds of passwords:

Document open password
A Report To open a PDF with an open password (also known as a user password), the user must enter a password.

Permissions password
To alter permission settings, a permissions password (sometimes known as a master password) is required.. You can restrict printing, editing, and copying of PDF content by using a permissions password. A password is not required for recipients to open the document in Reader or Acrobat. To change the restrictions you’ve set, they’ll need a password.

If the PDF is protected by both types of passwords, it can be opened with either. Only the permissions password, however, allows the user to change the restricted features. Setting both types of passwords is often advantageous due to the added security.

Add a Password to a PDF

One-click option to protect a PDF with a password

  1. Launch Acrobat DC and open the PDF.
  2. Choose File Protect Using Password. Alternatively, go to Tools Protect Protect Using Password.
  3. Choose whether you want to set password for viewing or editing the PDF.

    How to Add Password to a PDF File Using Adobe Acrobat DC
    Credit: Adobe
  4. Type and re-enter your password. Your password must contain at least six characters. The password strength is shown next to your password to indicate whether it is weak, medium, strong, or best.
  5. Click Apply. Acrobat displays a message confirming that the file was successfully password-protected.
    How to Add Password to a PDF File Using Adobe Acrobat DC
    Credit: Adobe
Advanced password protection
  1. Open the PDF in Acrobat DC, and do one of the following:
    Choose Tools > Protect > More Options > Encrypt with Password.
    Choose File > Protect Using Password, and then choose Advanced Password Protection from More Options.
  2. If you receive a prompt, click Yes to change the security.
  3. Select Require A Password To Open The Document, then enter the password in the appropriate field. Your password must contain at least six characters. The password strength meter evaluates your password and displays the password strength for each keystroke.

    How to Add Password to a PDF File Using Adobe Acrobat DC
    Credit: Adobe
  4. Then, from the Compatibility drop-down menu, choose an Acrobat version. Choose a version of Acrobat or Reader that is equal to or lower than the recipients’ version.

    How to Add Password to a PDF File Using Adobe Acrobat DC
    Credit: Adobe
    Note: The Compatibility option you choose determines the type of encryption used. It is important to choose a version compatible with the recipient's version of Acrobat or Reader. For example, Acrobat 7 cannot open a PDF encrypted for Acrobat X and later.
    
    -Acrobat 6.0 And Later (PDF 1.5) encrypts the document using 128-bit RC4.
    -Acrobat 7.0 And Later (PDF 1.6) encrypts the document using the AES encryption algorithm with a 128-bit key size.
    -Acrobat X And Later (PDF 1.7) encrypts the document using 256-bit AES. To apply 256-bit AES encryption to documents created in Acrobat 8 and 9, select Acrobat X And Later.
  5. Select an encryption option:
    Encrypt All Document Contents: Encrypts the document and the document metadata. If this option is selected, search engines cannot access the document metadata.
    Encrypt All Document Contents Except Metadata: Encrypts the contents of a document but still allows search engines access to the document metadata.
    Encrypt Only File Attachments: Requires a password to open file attachments. Users can open the document without a password. Use this option to create security envelopes.
  6. Click OK. At the prompt to confirm the password, retype the appropriate password in the box and click OK.
Remove Password Security

If you have the necessary permissions, you can remove security from an open PDF. If the PDF is protected by a server-based security policy, it can only be changed by the policy author or a server administrator.

  1. Open the PDF, then select Tools > Protect > More Options > Remove Security.
  2. Your options differ depending on the type of password security associated with the document.:
    – If the document only had a Document Open password, click OK to remove it.
    – If the document required a permissions password, type it in the Enter Password box and click OK. Click OK once more to confirm this action.

That’s it. Now, you can protect a PDF and remove its password protection by yourself easily.