How to add some content to all posts? Easy, install this plugin to your website/blog. When activated, a new option in the Posts menu will be able, Add To Post Footer option. Click there and insert the content what you want to add to all posts footer. Save it and it’s done. As you activate the plugin, all posts will have the content. If you don’t want more the content, just deactivate the plugin.

Add To Post Footer

Add some content to the bottom of all your posts. You can add images and HTML too. Install and activate it, it's easy!

SOGO

Tested with Gutenberg
Create a simple way to add javascript code to individual page post or custom post type header and footer, 
for example: add conversion code to thank you pages 
add google re-marketing code to individual pages 
and much more… 
added in version 1.3 the option to add script \ style to all pages not only individual pages, 
 this will allow you to add Google re-marketing code to the entire site or Google Analytics 
 to use it goto “settings” – “Header Footer Settings”
New Features (version 3.0): 
Added option for terms / category pages
New Features (version 2.3): 
 Added support for WooCommerce shop page.
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we support now exclude individual pages form printing the header and footer scripts, this is supported by 2 checkboxes in each page\post 
buy check it the script will not be display on this page
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we added support to limit the script only for certain post type \ page
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if you like it \ use it – please rate us.
usage: 
You need to paste the code with the script tag, for example: 
 you js code

SOGO Add Script to Individual Pages Header Footer

Simple plugin to add script to header and footer for individual pages & posts

Add To Post Footer vs SOGO Add Script to Individual Pages Header Footer