All images in my converted document are saved as one large background image and I am unable to move them independently. Why is that?

Graphics are saved to the background as a default setting in order to best preserve the original PDF document page layout. You can change these settings using the graphics handling options available in the Conversion Options dialog under the "View" menu – this may allow you to move individual images separately from the background.

This article refers to Able2Extract and Able2Extract Professional.