Can I password protect a PDF without having to open it first?

It can also be done using a stand-alone application, independently of Acrobat.

Hello olivias15744639

As per the description above, you want to protect a PDF file without opening it, Is that correct?

Protecting a PDF file without opening is not possible with Acrobat. You can protect a PDF file with password after opening it. For detailed information refer to Protect PDF files with permissions |  Link: https://helpx.adobe.com/in/acrobat/how-to/security-permissions-protect-pdf-files.html

PDF passwords, protected PDFs, file permissions | Adobe Acrobat DC Link: https://acrobat.adobe.com/in/en/acrobat/how-to/pdf-file-password-permissions.html

Feel free to update this discussion for any further assistance.

Regards,

Anand Sri.