Converting InDesign documents
From INDD to INX/IDML
To edit InDesign documents in Across, these must be provided in the InDesign exchange formats INX (InDesign Interchange Format) or IDML (InDesign Markup Language).
Therefore, a normal InDesign document in INDD format must be converted to an INX or IDML document before you can process it in Across. Simply open the INDD document in InDesign and export it to the INX or IDML format. To do this, open the document in InDesign, click File > Export, and select the InDesign Interchange format (INX) or the InDesign Markup format (IDML) from the drop-down list File type. Then click Save. You now have an INX or IDML file that you can check into Across and process in the usual manner.