Add default_content for pages

Hi,

How can I set default_content filter for pages using this plugin?
I put the code below in ‘functions.php’ in my site template.

add_filter( 'default_content', 'my_content_editor', 10, 2);

function my_content_editor($content) {
   // do something with $content
   return $content;
}

The above code works for posts but not pages. If the advanced page manager plugin is disabled it works for pages too. Which of the plugin files should I add the code to get this working?

Thanks in advance.

https://www.ads-software.com/plugins/advanced-page-manager/