Do all the documents that are required to be submitted in project management add any value to successful completion of project?

short answer id yes, but in SMB i think not all documents requierd. for lagr project you will need all PM document to avoid any misunderstanding nor project delay

The documents created add value so long as they

1. do not contradict with each other and

2. they serve the scope/spirit of the assignment

3. are in simple and relevant language which the stakeholders can understand, relate with and implement

As long as these are required and incorporated in the approved project plan, then yes, they are required for the successful completion of the project.

yes, by principle of quality management system, all documemts for that matter add value to the completion of the project as well as a contributing factor in the successful completion of the project. Otherwise, if we fail to document  something relevant to the closeout of the project such will create a problem later on.