copying the value of a form's file input field to another form's input field

You can't move the value of one file input to another. Instead, clone the input, place the clone where the original is, and move the original into the hidden form.

$(".inputfield1").change(function(){
  var $this = $(this), $clone = $this.clone();
  $this.after($clone).appendTo(hiddenform);
});