Password protection of your PDF file ensures that the PDF can only be opened by the intended recipient of the file. Password protection can also be used to prevent users from printing or editing the document. These settings can be further tweaked to allow only low resolution printing, and varying degrees of editing.
To password protect your PDF document in Adobe Acrobat Reader,
- Go to Advanced > Security > Encrypt With Password.
- A prompt will appear asking if you are sure you want to change the security settings.
- Click on Yes.
- Select Encrypt all document contents, check Require password to open document, and enter the password in the “document open password” field.
- If you want control on the permissions to print and edit the document, check Restrict editing and printing.
- Provide the password for changing these settings.
- Make sure Enable copying of text, images, and other content is unchecked.
- Click on OK.
A prompt will appear asking you to confirm the passwords you have entered. Another prompt states clearly that not all third-party programs respect the security settings in the PDF file. In this way you can lock or password protect your PDF file to ensure security and prevent unauthorized editing.
Also check out our article on how to crack or remove this security of PDF files or documents using third party software..