Hi,
It doesn`t seem like a good idea, to pass twice the same variable ls_null in you function call.

Try the code I post below. (you`ll have to change the initial value of ls_initialDir (c:\temp), to the default directory of your choice).
After you fill in a filename in the dialog when you run the code, ls_path will hold the path+filename and ls_file only will hold the file name.

string ls_path, ls_file, ls_initialDir, ls_title
int li_rc

ls_title = "Save as ..."
ls_initialDir = "c:\temp"
ls_path = ls_initialDir + "\*.pdf" // adding *.pdf, will make "*.pdf" appear in the "filename", but is not necessary. The extension will be added when you close the window anyway.

// passing in 32770 to get an Explorer style dialog instead of the outdated windows 3.11 version:
li_rc = GetFileSaveName ( ls_title, ls_path, ls_file, "PDF", "PDF Files (*.pdf),*.pdf, All Files (*.*),*.*", ls_initialDir, 32770)

regards