Password bypassed in client's PDF

[peterg9299518]

Hi, I have an issue with a document I sent to a client yesterday. The document was sent with password protection.  My client says that when she clicked on the link to open the document, it was there, already opened having bypassed the required password.  I rechecked in my system and when I try to open the document at my computer it DOES require the password.  I use a Windows10 computer.  My client received her email on a Mac. Do you have any ideas?  Thank you.