the command name is acroread. to run it you need to:
1. have the /usr/local/Acrobat5/bin directory in your PATH
2. create a link to /usr/local/Acrobat5/bin/acroread in a directory that is in your path see "man ln"
or 3. copy acroread (which is only a short shell script to a directory in your path (say usr/bin)
then you will probably need to modify acroread (use a text editor like gedit) to add a line that reads "LANG=C"
this is a patch for redhat. See: http://www.adobe.com/support/techdocs/2eeea.htm
this should allow you to type "acroread filename" to view filename from a shell prompt.
then if you want your graphical shell to automatically start acroread when you select (double click) a .pdf you need to modify the file type configuration.
try preferences/file types from your redhat menu.