if room=main { //Checks the room. Change it to your room where you pause the game.
//If there are many rooms where it has to pause then: if room=main or room=main2 ...

if keyboard_check_pressed(vk_space) { //Checks the pausing key. You can change this too.
screen_save('pause.bmp') //Takes a picture of the screen.
global.bg = background_add('pause.bmp',0,0,1) //Loads it to the game.
game_save('pause') //Saves game.
global.pauseroom = room_add(); //Adds a new room for the pause.
room_instance_add(global.pauseroom,0,0,obj_pause) //Places obj_pause in that room.
room_set_background(global.pauseroom,0,1,0,global.bg,0,0,0,0,0,0,1) //Sets the room's background.
room_set_caption(global.pauseroom,'Pause Example - *paused*') //Sets the caption of the screen. (if you don't want this you can remove this line.)
room_goto(global.pauseroom) //Goes to that room.
}
}
else { //If room is not main. (if the game is paused)
game_load('pause') //Loads the game. (unpause)
if file_exists('pause.bmp') { file_delete('pause.bmp') }  //Deletes the file that is not needed anmore.
}