Search for page number with PDF Expert and Applescript
PDF Exper and keystroke "42" doesn't work for me.

However, using Skim and key code works:

do shell script "open -a Skim agile.pdf"
delay 0.1

tell application "System Events" 
  tell application process "Skim"
    tell application "System Events" to tell process "Skim" to click menu item "Go to Page…" of menu "Go" of menu bar 1
    delay 0.1
    key code {21, 19, 36}
  end tell
end tell