Sorry, “not working” doesn’t tell us anything. Please edit your topic title to be clear and concise about the issue you’re having.
What did you edit? You should normally not edit that file as it’s automatically generated.
Either way, you posted the wrong section of the file. application/pdf is under [Added Associations], not [Default Applications].
By the way, there’s no reason to post a whole section of the file if all you’re concerned about is one file type. grep is your friend. 
Example on my system:
❯ grep pdf ~/.config/mimeapps.list
application/pdf=org.gnome.Evince.desktop;
In the future, please use proper formatting, using blockquote for terminal or file output is not appropriate. Neither is posting screenshots. I’ve removed your screenshot above.
Tip: The more effort you put into your topic, the more effort helpful volunteers will provide.
Please see: