You can create a module by using module item template provided in VS 2010 or above, then add your documents in the solution and provision the documents through that module. Then you have the following two options.
If you add this module into the package by using package designer provided by Visual Studio. Then, whenever you would deploy the webparts wsp/package, these documents would be deployed.
If you want the documents to be updated by feature then instead of adding the module in package add the module to the feature of webparts. So, whenever the feature would be activated these documents would be updated.