The file name, as depicted in the bottom left corner of the viewer panel, is typically the file name used when exporting a document via Workflow (namely to a Web Service).

This can be problematic, when, for instance, a web form produces a document that goes into a workflow. In this case, the web form produces a file with the file name "form-name.pdf" where the name of the form is "Form Name". This can cause issues if the service in question expects different documents to have different names, or if the user has set the document name within DocuWare with a database field.