pdf files

Hello I have a user that has adobe acrobat 7 and adobe reader 8. Anytime the user opens a pdf file it dfaults to the adobe reader 8. The user would like to be able to edit the pdf files so all pdf files need to open with acrobat 7 instead of the adobe reader 8. This was not happening with adobe reader 7 before. Should I uninstall adobe reader 8 and reinstall version 7. Or is their a way to make all pdf files that the user receives to open with the acrobat 7.
Thanks,
Eddie