When exporting the model to CAD format or DWF, you can specify a name or a prefix for the exported files.
First open the related Export dialog: click File tab 
ExportCAD Formats, and select the desired format for export. Specify the export setup, view/sheet set, and other settings, and click Next.
The Export dialog displays the following fields:
File name/prefix
When exporting multiple files, for File name/prefix, enter a common prefix for the exported files. For Naming, select the appropriate option.
For example, if you are exporting the Level 1 floor plan and north elevation views to DWG files and you enter the prefix Country House, the resulting exported file names are Country House Elevation North.dwg and Country House Floor Plan Level 1.dwg.
To specify the name of a single export file, enter the file name. For Naming, select Manual.
Naming
In the Export dialog, for Naming, use one of the following options to name the exported files:
-
Automatic - Long (Specify prefix). Manually specify a prefix in the File name/prefix text box, or accept the default, which uses the format:
Revit Sheet/View: Project Name-View Type-View Name
-
Automatic - Short.
Revit determines the name automatically and adds a prefix to the file name of the current view or multiple views and sheets. The format is:
Revit Sheet: Sheet Name or Revit View: View Type-View Name
- Manual (Specify file name). Manually specify the entire file name in the File name/prefix field.