In this scenario the user has a Solid Edge drawing with multiple sheets.
They then export the drawing as a DXF - in this case they define AutoCAD 12 as the version, as the third party software that they will be importing the DXF into can only read version 12 compatible files.
As they have a multi-sheet drawing they also select the "All Sheets to same file" option.
However when they open the DXF file they see only one sheet - the sheet that was active when the drawing was exported.
The reason for this is that AutoCAD version 12 - as well as versions 13 and 14 - do not support multi-sheet drawings.
Therefore, the user will need to use either 'Active sheet only' or 'All sheets to separate files' for their sheet options.