uses ComObj;
      .....

   procedure TForm1.Button1Click(Sender: TObject);
   var
     NVresize : Variant;
     retVal : Integer;
   begin
     NVresize := CreateOleObject('PDFresize.Neevia');
 
     NVresize.Paper := 'letter';
     NVresize.Orientation := 2;
     NVresize.Scale := false;
 
     retVal := NVresize.resizePDF('c:\in.pdf', 'c:\out.pdf');
     if retVal <> 0 then
       Application.MessageBox(PChar('Error code=' + IntToStr(retVal)),'',0)
     else
       Application.MessageBox('Done','',0);
   end;