问如何修复“第72行的错误:错误: sh: img2pdf:命令未找到”

EN

//Clean sender
function cleanSender(sender) {
  var pos = sender.search("<");
  return sender.slice(0, pos - 1);
}
//Num to string, padding included
function numToString(num) {
  if(num < 10) {
    return '0' + num.toString();
  }
  else {
    return num.toString();
  }
}
//date to time stamp
function genTimeStamp(date) {
  if (!(date instanceof Date)) {
    console.log('Type Error!');
    return undefined;
  }
  var hours = numToString(date.getHours());
  var minutes = numToString(date.getMinutes());
  var seconds = numToString(date.getSeconds());
  var month = numToString(date.getMonth() + 1);
  var day = numToString(date.getDate());
  var year = numToString(date.getFullYear());
  var timeStamp = month+day+year+hours+minutes+seconds;
  return timeStamp;
}

function run() {
  var mail = Application('Mail');
  var finder = Application('Finder');
  var app = Application.currentApplication();
  var keyword = "Test";
  var topFolderPath = "/Users/CatLover/Documents/HWBox";
  var topFolder = finder.startupDisk.folders.byName("Users").folders.byName("CatLover").folders.byName("Documents").folders.byName("HWBox");
  mail.includeStandardAdditions = true;
  finder.includeStandardAdditions = true;
  app.includeStandardAdditions = true;
  var messages = mail.inbox.messages;
  var messagesLength = messages.length;
  for(let i = 0; i < messagesLength; i++) {
    let message = messages[i];
    if (message.subject().includes(keyword) && message.mailAttachments().length != 0) {
      var sender = cleanSender(message.sender());//Name only
      var timeStamp = genTimeStamp(message.dateSent());//Folder name
      var attachments = message.mailAttachments();
      var individualPath = topFolderPath + '/' + sender;
      if (!finder.exists(Path(individualPath))) {
      //No folder!
        finder.make({new: "folder", at: Path(topFolderPath), withProperties:{name: sender}});
      }
      var messagePath = individualPath + '/' + timeStamp;
      if (!finder.exists(Path(messagePath))) {
      //No folder!
        finder.make({new: "folder", at: Path(individualPath), withProperties:{name: timeStamp}});
        var command = "img2pdf ";
        var attachmentsLength = attachments.length;
        for(let j = 0; j < attachmentsLength; j++) {
          let attachment = attachments[j];
          var filename = attachment.name();
          var filePath = messagePath + '/' + filename;
          mail.save(attachment, {in: Path(filePath)});
          command = command + filePath + ' ';
        }
        if (attachmentsLength > 1) {
          //Pics
          var pdfName = sender + timeStamp;
          command = command + '-o ' + messagePath + '/' + pdfName;
          app.doShellScript(command);
        }
      }
      else {
        continue;//Non-spammers aren't going to send two emails at the same time down to the same second. No need to process an already processed email.
      }
    }
  }
}