Generally there is no such download. As long as you have your serial number, you may be able to get help from Adobe (they are not here in general). I am not sure if the CD is locked to a specific number. If not, you might be able to borrow a copy from a friend and reinstall with your number.
So, the CD drive on my laptop no longer functions, so how can I install a valid copy of Acrobat 9? How can you help me download it?