You can try to change the file associations of your system to use the Reader application (check whatever OS you are using's help files for instructions) but it doesn't always work. Basicaly, it's not recommended nor supported to have both installed since they share many resources and can get confused easily.
Thank you. I found some information on line where many people had
encountered the same problem with Adobe 9 version and said to uninstall
that and download the 8.1.2 version. Their problem was similar to mine,
but they did not have another Adobe software on their computer in
addition to Reader. I did as they said and it now works just fine.
so both application will conflict?
Yes although you could get lucky and not have problems. That's why it's not supported. Works for some but not for others and for the ones that it doesn't work for, troubleshooting the exact problem is almost impossible.
Yes. However, I got online and found others that said the same thing
happened to them. They uninstalled Reader 9.1 and installed 8.2. It
works fine. Must be something in Reader 9 that is conflicting.