OrthoGraph has an integrated DXF export functionality directly from the iPad, which is the native file format of AutoCAD. The produced DXF file is a 2D output of the selected floor plan. If you would need a 3D output, then either use IFC (Industrial Foundation Class) or the dedicated conversion tool that is compatible with ArchiCAD. Latter is an Add-On to ArchiCAD that lets you open OrthoGraph's native file format: SRVD.
For further details please follow this link: http://www.orthograph.net/orthograph-cad-export/