Save to PDF changes ≤ to =

I have a report that previews and prints correctly but when I save it to a PDF document some of the characters change.

The preview shows the character ≤ correctly, but when I save to PDF its changed to a = symbol.

What is really strange if I have the Ω symbol in the same text field it does not change.

Anyone else had similar issues with PDF and is there a easy fix ?

Thanks
Ian