This might be a silly question but does DuplicateFileDocument actually create a new file in the Mendix system/db? Or does it simply do it within memory? Our backup has been increasing in size dramatically and I have a feeling DuplicateFileDocument is literally creating a duplicate document that is included in our backups. If it really does create an actual copy I am wondering why the original Mendix Developer chose to use it because all the MicroFlow does is save it out to a backup. But I think it might be saving 2 copies in the db.
The FileDocument entity is always committed and does not live in memory, however file documents are not actually saved in the database but rather in the File Storage space of the Mendix Cloud. Duplicating the documents should not dramatically increase the size of your database, but it would increase the size of your file storage as seen in the ‘Application File Storage’ graph in the Mendix portal. This would cause your backups to grow in size. It sounds like the duplication may be unnecessary as you could probably just save out the original file.