Prevent people from sending/sharing my pdf files.

Is there a way to prevent people from sending/sharing my pdf files other than by password protection? These are files that must be easily readable (so no password on every file) by the client but not forwarded or shared with others.

They must be able to download the file from my website or email, they are allowed to print it, but not to send or share it with anyone.

Is this possible? It doesn't seem to be from what I have read on the subject.