input: Write a python function to convert a Word document to a PDF using win32com.client.
  assert convert_to_pdf('example.docx', 'output.pdf') == 'output.pdf'
  assert convert_to_pdf('sample.docx', 'sample_output.pdf') == 'sample_output.pdf'
output: def convert_to_pdf(input_docx, output_pdf):
      import win32com.client
      
      word = win32com.client.Dispatch('Word.Application')
      word.Visible = False
  
      doc = word.Documents.Open(input_docx)
      doc.SaveAs(output_pdf, FileFormat=17)  # 17 is the code for PDF format
      doc.Close()
  
      word.Quit()
      
      return output_pdf