Post Per Page For Portfolio

Yes “posts_per_page” can change the number of posts shown.
Where can you add it to your code?
You can add this parameter to your $args variable.

To add it to your $args variable you can do this:

$args = array(
    'post_type' => 'portfolio', 
    'posts_per_page' => 12
);

“12” is the number of posts per page that will be shown. Change this whatever number you want.

You can read more about “posts_per_page” here