Display file text one page at a time, wait 20 seconds, then auto-advance

This fairly standard awk should be ok on AIX

awk '{if(NR>1 && NR%24==1)system("sleep 20");print}'

As mentioned in the comments, if you want to exit on interrupt, you can replace the system() by

{if(system("sleep 20"))exit}

but it might not work on your OS.

#!/usr/bin/env expect 
set timeout 20
spawn -noecho man autoexpect
while 1 {
  expect {
    timeout { send " " }
    -ex "(END)" { exit }
  }
}