How to Password-protect an Existing PDF

Portable document format, or PDF, files are a great way of sharing information across the Internet. If you have a full version of Adobe Acrobat, you can password-protect your PDF files so that unauthorized users are unable to access them. You can then send sensitive or personal information by email, safe in the knowledge that only you and those to whom you have given your password will be able to access the files.

...
Secure your PDF files with a password.

Step

Double-click on the PDF document that you wish to secure with a password to open it using Adobe Acrobat.

Step

Select "Secure" from the taskbar menu.

Step

Select "Password Encrypt" or "Encrypt with password" from the drop-down menu -- the exact wording will depend on which version of Adobe Acrobat you are using -- and click "Yes" on the confirmation dialogue box to bring up the "Password Security Settings" screen.

Step

Choose which earlier version of Adobe you wish your document to be compatible with from the list of options at the top of the menu box.

Step

Click the "Require a password to open the document" check box. Choose your password and type it in.

Step

Click the next check box to choose whether to allow people to print or make changes to your document. If you choose to allow these privileges, you will need to add a second, separate password. If you are happy to allow some printing and editing options, choose them from the drop-down menus.

Step

Click "OK" to save your changes. Your document is now protected with a password.