code: func ComparePDFFiles(file1Str, file2Str string, printDiff bool) (err error) {
  	var sl1, sl2 []byte
  	sl1, err = ioutil.ReadFile(file1Str)
  	if err == nil {
  		sl2, err = ioutil.ReadFile(file2Str)
  		if err == nil {
  			err = CompareBytes(sl1, sl2, printDiff)
  		} else {
  			// Second file is missing; treat this as success
  			err = nil
  		}
  	}
  	return
  }
docs: // ComparePDFFiles reads and compares the full contents of the two specified
  // files byte-for-byte. Nil is returned if the file contents are equal, or if
  // the second file is missing, otherwise an error.