The file format to save an assembled document to. FileFormat.unspecified is the default.
When the value of this property is not specified, DocumentAssembler behaves as follows:
When you specify a file path to save an assembled document, the save file format is determined from the file extension of the path.
When you specify a stream to save an assembled document, the save file format remains the same as the file format of the loaded template document.
Beware that it is not always possible to save an assembled document to any file format using GroupDocs.Assembly. For example, a document loaded from a Word Processing format (such as DOCX) cannot be saved to a Spreadsheet format (such as XLSX). See the GroupDocs.Assembly online documentation for supported load‑save format combinations.