Change Printing Orientation during middle of print job.

Have a look at following function in MyPrintView.CPP :

LPDEVMODE CMyPrintView::ChangeDevMode(HWND hWnd, char *pDevice)
{
   HANDLE      hPrinter;
   LPDEVMODE   pDevMode;
   DWORD       dwNeeded, dwRet;

   /* Start by opening the printer */
   if (!OpenPrinter(pDevice, &hPrinter, NULL))
       return NULL;

   /*
    * Step 1:
    * Allocate a buffer of the correct size.
    */

   dwNeeded = DocumentProperties(hWnd,
       hPrinter,       /* handle to our printer */
       pDevice,        /* Name of the printer */
       NULL,           /* Asking for size so */
       NULL,           /* these are not used. */
       0);             /* Zero returns buffer size. */
   pDevMode = (LPDEVMODE)malloc(dwNeeded);

   /*
    * Step 2:
    * Get the default DevMode for the printer and
    * modify it for our needs.
    */
   dwRet = DocumentProperties(hWnd,
       hPrinter,
       pDevice,
       pDevMode,       /* The address of the buffer to fill. */
       NULL,           /* Not using the input buffer. */
       DM_OUT_BUFFER); /* Have the output buffer filled. */
   if (dwRet != IDOK)
   {
       /* if failure, cleanup and return failure */
       free(pDevMode);
       ClosePrinter(hPrinter);
       return NULL;
   }

   /*
    * Make changes to the DevMode which are supported.
    */
      if (pDevMode->dmFields & DM_ORIENTATION)      
      {
       /* if the printer supports paper orientation, set it*/
       pDevMode->dmOrientation = DMORIENT_LANDSCAPE;      
      }
   /*
    * Step 3:
    * Merge the new settings with the old.
    * This gives the driver a chance to update any private
    * portions of the DevMode structure.
    */
   dwRet = DocumentProperties(hWnd,
       hPrinter,
       pDevice,
       pDevMode,       /* Reuse our buffer for output. */
       pDevMode,       /* Pass the driver our changes. */
       DM_IN_BUFFER |  /* Commands to Merge our changes and */
       DM_OUT_BUFFER); /* write the result. */

   /* Done with the printer */
   ClosePrinter(hPrinter);

   if (dwRet != IDOK)
   {
       /* if failure, cleanup and return failure */
       free(pDevMode);
       return NULL;
   }

   /* return the modified DevMode structure */
   return pDevMode;

}

-MAHESH