Compressing PDF is all about reducing the size of the file, usually if you check through google you will find free platforms that compress your PDF file for you free, the outcome is that the fonts, images on such documents are reduced with little or no noticeable effect. Another way of reducing the file size is convert it MS words, then reduce the font size of the character before finally converting back to PDF, but the best option is to check those platforms on google for free compression.