1. A preflight system for analysing an electronic document for possible problems, the document being created using a creation application that has a plurality of output components for outputting the document, the preflight system comprising: a plurality of preflight clients distributed within the document creation application to reside closely associated with the output components of the creation application, each preflight client being provided for an associated output component of the creation application and having testing code for testing one or more warnings relating to the associated output component, the testing code being implemented in a portion of the creation application that has direct access to relevant information of the associated output component for testing the warnings; a registry to register the preflight clients and store a list of warnings that each of the preflight clients test; and a central preflight engine capable of communicating with the preflight clients, the preflight engine automatically determining based on the registry, among the preflight clients, one or more relevant preflight clients that are relevant for one or more selected output components which are to be used to output a document created by the creation application, centrally controlling preflight process on the document by using the relevant preflight clients which test the warnings within the creation application based on a native document format of the creation application prior to outputting the document from the creation application by the selected output components, and centrally collecting information on test results of the warnings from the relevant preflight clients for the selected output components prior to outputting the document from the creation application.