You have a module, which create files you want to integrate into Workflows?
PDFMaker and SQLReports are implemented in this way!
If you create a similar module you could create a interfacefile to attach this files to Mails, Store as Documents or simple use the file in every task, which could handle files in any way.
Create a files in modules/Workflow2/extends/interfaceFiles/ with the filename <individual>.inc.php.
This file must include a Class, which extends from WorkflowInterfaceFiles.
You must implement the following structure to be recognized by Workflow Designer:
[prism field=filesource1 language=php]