Open the PDF in Acrobat, and do one of the following:

• Choose File > Protect Using Password.
  
• Choose Tools > Protect > Protect Using Password.

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

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.

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

Open the PDF in Acrobat, 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.

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

Select Restrict Editing And Printing Of The Document.

All Adobe products enforce the restrictions set by the permissions password. However, if third-party products do not support these settings, document recipients are able to bypass some or all of the restrictions you set.

Type the password in the corresponding field. 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 what the user can print from the Printing Allowed menu:

Prevents users from printing the document.

Lets users print at no higher than 150‑dpi resolution. Printing may be slower because each page is printed as a bitmap image. This option is available only if the Compatibility option is set to Acrobat 5 (PDF 1.4) or later.

Lets users print at any resolution, directing high-quality vector output to PostScript and other printers that support advanced high-quality printing features.

Select what the user can change from the Changes Allowed menu:

Prevents users from making any changes to the document that are listed in the Changes Allowed menu, such as filling in form fields and adding comments.

Lets users insert, delete, and rotate pages, and create bookmarks and thumbnails. This option is only available for high (128‑bit RC4 or AES) encryption.

Lets users fill in forms and add digital signatures. This option doesn’t allow them to add comments or create form fields. This option is only available for high (128‑bit RC4 or AES) encryption.

Lets users add comments and digital signatures, and fill in forms. This option doesn’t allow users to move page objects or create form fields.

Lets users edit the document, create and fill in form fields, and add comments and digital signatures.

Choose any of the following options:

Lets users select and copy the contents of a PDF.

Lets visually impaired users read the document with screen readers, but doesn’t allow users to copy or extract the document’s contents. This option is available only for high (128‑bit RC4 or AES) encryption.

Select an Acrobat version from the Compatibility menu. Choose a version equal to or lower than the recipients’ version of Acrobat or Reader. 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.

Select what you want to encrypt:

Encrypts the document and the document metadata. If this option is selected, search engines cannot access the document metadata.

Encrypts the contents of a document but still allows search engines access to the document metadata.

Requires a password to open file attachments. Users can open the document without a password. Use this option to create security envelopes.

Click OK. At the prompt to confirm the password, retype the appropriate password in the box and click OK.

Open the PDF, then select Tools > Protect > More Options > Remove Security.

Your options vary depending on the type of password security attached to the document:

• If the document had only a Document Open password, click OK to remove it from the document.
• If the document had a permissions password, type it in the Enter Password box, and then click OK. Click OK again to confirm the action.