Open the PDF in a PDF editor or viewer that has permission to remove security
Enter the document password if prompted
Go to File or Document Properties
Open the Security or Permissions section
Change the security method to None or No Security
Save the PDF as a new file
If you know the password, use an online or desktop PDF unlock tool that supports authorized removal
If the PDF has owner restrictions, use the owner password to remove them
If the PDF is digitally signed or protected by DRM, contact the document owner for access
If you do not have permission, request an unlocked copy from the sender