Adjusting:
  
  You adjust the image with the Property Inspector.
  Window/Properties or Modify/Select Properties.
  
   
 
You can scale it with 
  the width (W) and Height (H) boxes or stretch the image with the handles around 
  the image.
  
You can set it back 
  to the original size with the "Reset Size" button.
  if you don't see all the options, use the expander button on the bottom 
  right of the panel.  
*note: changing the image 
  size does not reduce the file size of the image, so if you find yourself scaling 
  down a lot use images closer to the size that you will want them to be.