To ensure the security of data, some PDF’s will have a password to protect it. How to open protected PDFs? If you have received a PDF that is protected with a password, you just need to enter the correct password to view the file.
Some protected PDF files have other restrictions to prevent from printing, editing, copying, etc. When you try to print or edit this secured PDF file, you will be notified that you are prohibited to do so without the permission password. You can click the "Enable Editing" button to enter the permission password to edit it.