Upvote:3
In general you need very, very strong arguments that the decision was wrong (given the information they had at the time) to be successful with an appeal. Remember: a visa is not something you're entitled to, it's something you can be granted if you can provide strong enough arguments that you should get one, and the staff at the embassy are basically free to decide either way they want to.
If you have to add additional documents, it's really not an appeal but a new application!
Just make sure you understand the reasons given, see e.g.
and address those issue in a new application.