I have to control PDF size based on their image or content quality, how it can be achieved using wkhtmltopdf shell utility tool.
Based on the help section you can use the --image-quality <integer> parameter to control the quality of the images. Replace <integer> with a number between 1 and 100 where 100 is the best quality. I would suggest trying 80, sometimes 70 still gives acceptable results but it depends on the image.