If I have an access database on a CD can I access it, add/change tables and
save back to the CD?
Not directly. A CD is not like a floppy disk.
Copy the database from the CD onto your computer.
Right-click on the database icon, and select properties.
Uncheck the Read Only Attribute.
You can now do anything you wish to the database on your computer.
When done, if you wish to save the database changes onto a CD, you
will have to burn it onto the CD, using the appropriate software.