Right Now jetpack provides only way to embed subscriptions as sidebar widget. Registering a new sidebar would be a better Idea to do so, and this will not take more than few seconds.
Step 1 – Register a sidebar for jetpack
Just drop in this code somewhere in your theme’s functions.php
file.
register_sidebar( array(
'name' => 'JetPack in page',
'id' => 'jetpack-in-page',
'before_widget' => '<div id="jetpack">',
'after_widget' => '</div>',
'before_title' => '<h3>',
'after_title' => '</h3>'
) );
Step 2 – Where you want the form to appear ?
Now place the following code where you want the form. Anywhere in the theme, You can put this code just bellow the <?php the_content(); ?>
So it will show just bellow your page / post content.
<?php dynamic_sidebar( 'jetpack-in-page' ); ?>
Step 3 – Your done !
Now drag and drop the widget into JetPack in page
sidebar and the form will be shown in the page. However the widget is specially made for sidebars so you might need to do some Styling to make it look nicer on full page.
Reference – register_sidebar();
(WordPress Codex)