You use something like this:

tell application "Adobe Acrobat Pro"
    activate
    set theDoc to active doc
    save theDoc to file filepath using conversion n
end tell

The value of n depends on the version of Acrobat: 11 for v7, 13 for v8, 15
for v9.

-- 
Shane Stanley <[log in to unmask]>
AppleScript Pro Sessions <http://scriptingmatters.com/aspro>