may be he/she wants to try. or just wanting to reduce any amount of pages.
but rishika920 it's true it will drop the quality of text to read. and most of the bad things is that it can probably mess up the layout of the text. after modifying. you must take it in mind.
most reliable option is that you print them on both sides of the page. you'll get half with no hardwork to find software or any other techniques to reduce the pages.
and if you already requested the quote after making it on both sides of page. for more extent, if you already made it from 1000 to 500 pages and considering to print on both sides. then it's fine. this is enough I think.