Print custom module in a block
Copy Print's print.tpl.php file into module folder, and name it print--node--foo.tpl.php.

function foo_theme_registry_alter(&amp;$theme_registry) {
    $theme_registry['print__node__foo']['template'] = 'print--node--foo';
    $theme_registry['print__node__foo']['path'] = drupal_get_path('module', 'foo');
}

Note: My module and content type share the same name of foo.