Set the permission flags on a PDF: whether readers may print it, copy text out of it, extract content, fill in forms, add annotations or modify the document. These flags are recorded in the file and honoured by well-behaved readers. It is worth understanding what they are and are not - they express intent, and they are not a technical barrier in the way encryption is.
They stop readers that choose to honour them, which covers most mainstream software. They are not enforced cryptographically, so a determined user with other tools can ignore them. Treat them as a statement of intent.
Encrypt it with a user password using Password Protect PDF. That is enforced by the encryption itself rather than by the reader choosing to cooperate.
Yes - that is exactly what the print permission does. Bear in mind the same caveat about enforcement.
Files are uploaded over an encrypted connection and processed on CoonTool's own server, not in your browser. The working copy is deleted automatically once the job is done, and in any case within 24 hours. Nothing is stored permanently and no account is required.