Securing PDFs with passwords Part 1

Securing PDFs with passwords Part 1

Password security basics

You can limit access to a PDF by setting passwords and by restricting certain features, such as printing and editing. However, you can't prevent saving copies of a PDF. The copies have the same restrictions as the original PDF. Two types of passwords are available:

Document open password A Document open password (also known as a user password) requires a user to type a password to open the PDF.

Permissions password A permissions password (the primary password) requires a password to change permission settings. Using a permissions password, you can restrict printing, editing, and copying content in the PDF. Recipients don’t need a password to open the document in Acrobat or Acrobat Reader. They do need a password to change the restrictions you've set.

If the PDF is secured with both types of passwords, it can be opened with either password. However, only the permissions password allows the user to change the restricted features. Because of the added security, setting both types of passwords is often beneficial.

Note

You can't add passwords to a signed or certified document.

Add a password to a PDF

One-click option to protect a PDF with a password:

  1. 1. Open the PDF in Acrobat. From the global bar in the upper left, select All tools > Protect a PDF > Protect with password. 

  2. 2. In the Protect Using Password dialog box, select if you want to set the password for viewing or editing the PDF.

    Protect using password

  3. 3. Type and retype your password. Your password must be at least six characters long. The password strength is displayed next to your password to indicate whether the chosen password is weak, medium, strong, or best.

  4. 4. Select Apply. Acrobat displays a confirmation message that the file was successfully protected using password.

    Protection confirmation message

Learn how to password protect a PDF using the Acrobat online tool to easily encrypt a PDF file and limit access to a document by setting a password.

Advanced password protection:


  1. 1. From the global bar in the upper-left, select All tools > Protect a PDF. From the Protect a PDF toolset in the left pane, select Encrypt with Password. 

  2. 2. If you receive a prompt, select Yes to change the security.

  3. 3. Select Require a password to open the document, then type the password in the corresponding field.

    Note

    Your password must be at least six characters long. For each keystroke, the password strength meter evaluates your password and indicates the password strength.

    Select Require a Password to Open the Document
    Password Security - Settings let you set a password to open a PDF

  4. 4. Select an Acrobat version from the Compatibility drop-down list. Choose a version equal to or lower than the recipients’ version of Acrobat or Acrobat Reader.

    Options control compatibility with previous versions and type of encryption
    Options control compatibility with previous versions and type of encryption

    The Compatibility option you choose determines the type of encryption used. It's important to choose a version compatible with the recipient's version of Acrobat or Acrobat Reader. For example, Acrobat 7 can’t 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. 5. Select an encryption option:

    Encrypt all document contents Encrypts the document and the document metadata. If this option is selected, search engines can’t 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.

    Note

    The iFilter and the Find or Advance Search commands of Acrobat don’t look into the PDF’s metadata even when you select the Encrypt all document contents except metadata option. You can use a search tool that takes advantage of XMP 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. 6. Select OK. Retype the appropriate password in the box at the prompt to confirm the password and select OK.

Restrict editing of a PDF

You can prevent users from changing PDFs. The restrict editing option prohibits users from editing text, moving objects, or adding form fields. Users can still fill in form fields, sign, or add comments.

  1. 1. Open the PDF in Acrobat. From the global bar in the upper left, select All tools > Protect a PDF > Protect with password. 

  2. 2. If you receive a prompt, select Yes to change the security.

  3. 3. Choose Editing, and then type and retype your password. Your password must be at least six characters long. The password strength is displayed next to your password to indicate whether the chosen password is weak, medium, or strong.

    Restrict editing

  4. 4. Select Apply. Acrobat displays a confirmation message that the file was successfully protected using the password.

    Restrict editing confirmation message
 

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