Try changing the Settings to print or press. I suspect the characters you are having problems with are not embedding and you do not have them on your system.
I too had this annoying issue, usually printing from https sites, although the site address may be coincidental.
What worked for me was:
- Select Print
- In the print dialog box, select Adobe PDF and then Preferences.
- In the Printing Preferences dialog box the tab should be Adobe PDF Settings
- Uncheck the box next to Rely on system fonts only; do not use document fonts
- Select OK
If the box is already unchecked, it might be caused by something similar. This worked so I went no further. I have not yet checked to see if this must be done each time or how to make it default.