Procedures:

For Acrobat Professional (Screen capture base on Acrobat Pro XI):

  • Open the PDF file.
  • Choose File -> Document properties from the menu bar.
  • Click on the security tab. Choose Password Security from Security Method.
    The image illustrate how to choose Password Security from Security Method in Acrobat Professional
  • Then tick the option Require a password to open the document and enter the password in the Document Open Password box. (We highly recommend you to set a STRONG password. You can refer to the indicator on the right.)
    The image illustrate how to set Password Security in Acrobat Professional
  • Re-enter the password when prompt.
  • You are recommended to use the STRONG password. You can refer to the indicator on the right.
  • Finally, save the file.

For Foxit:

  • Open the PDF file.
  • Click the "Protect" tab. Then choose "Password Protect" from "Secure Document".
    The image illustrate how to choose Password Security from Security Method in Foxit

    The image illustrate how to choose Password Security from Security Method in Foxit
  • Then check the option "Require a password to open the document" and enter the password in the "Password input" box.
    Re-enter the password in "Password Confirm" box
    Click "OK" (We highly recommend you to set a STRONG password. e.g. Password with more than 8 characters, consisting of both alphabets and numbers.)
    The image illustrate how to set Password Security in PDF-XChange
  • Finally, save the file.