In fact it may make them worse - it may just cause the surfaces to glaze.
Badly worn discs can cause squealing whereby a radius is formed at the inner or outer edge of the disc and this small contact area can cause vibration of the pad.
Brake manufacturers do NOT recommend using anti-seize compounds such as copper grease on the back of brake pads. There are other specialist compounds especially for this purpose.
A few years back I emailed the technical manager of APEC Braking and he replied clearly stating copper grease, etc should not be used. I would reproduce it here but sadly I lost his email after a computer glitch.