CAD tip # 12347:

Error in drawing header on line 1.
Invalid or incomplete DXF input -- drawing discarded.
Press ENTER to continue:

This error indicates that the opened DXF file is corrupted (damaged). Common causes are:

• The DXF file was created by an external application but it doesn't have a proper format matching the DXF specification.
• The file was created as an export from a corrupted (e.g. non-Autodesk) DWG file.
• The file was damaged during transmission or during copying.
• It is not a DXF file, but e.g. a renamed .DWG file.
• The DXF file was edited in Word.
• The DXF file is not stored in the ASCII or UTF-8 (w/o BOM) format - it is stored e.g. in the text format encoded as UTF-16 or as UTF-8 with the leading BOM characters.

Try to create the DXF file again or repair it using a text editor, e.g. Notepad, Notepad++.

A typical DXF file (after you open it in Notepad) begins e.g. with this:

  0
SECTION
  2
HEADER
  9
$ACADVER
  1
AC1032
  9
$ACADMAINTVER
 90
      157
  9
$DWGCODEPAGE
  3
ANSI_1250
  9
$LASTSAVEDBY
...