Add the PrintFriendly & PDF Button to Categories in WordPress

Open the pf.php file in your plugins folder.  Plugins > printfriendly > pf.php

In pf.php, find the function "category_included".

function category_included() {

    //  return ( 'all' === $this->options['category_ids'][0] || in_category($this->options['category_ids']) );

    return true ;

}
 

Include in Categories

function category_included() {

   return in_category(array(101,102,103));

}

 

Exclude in Categories

function category_included() {

   return !in_category(array(104,105,106));

}