When working with DWF, it helps to understand a little about the AutoCAD PLOT command. The PLOT command takes the data from model space or a layout and directs it to the device identified by a Plotter Configuration (PC3) file.
In terms of DWF file generation, there is an ePlot DWF6 PC3 file that can be specified instead of a specific plotting device:
The settings for the DWF6 ePlot PC3 file can be configured to generate one multisheet DWF file or one separate DWF file per layout. The optimal process is to create one multisheet DWF file allowing the user to send only one file to a commercial reprographic shop for printing.