What is the format of the file downloaded via API?

Greg, thank you for your prompt response. I fully understand that there is no issue with Dropbox API and response (let's call it fileBuffered) that I get on my server-side is accurate. Regardless is I send "Content-Type", "application/pdf" or "Content-Type", "application/octet-stream" I get a strange response on my client-side

The fileBuffered size on a server-size is 132,597. The some how it grows to 254Kb when sent to a client-side. It is clear that there is no issue with Dropbox API but maybe you know how to tacke the issue?

Server-side

const file = fileBuffered;
res.setHeader("Content-Type", "application/stream-octet");
res.send(file);

Client-side

function documentFileDownload(fileName) {
   const ip = location.host;
   let request = $.ajax({
      type: "POST",
      url: `${http() + ip}/documentFileDownload`,
      headers: {
         "Accept": "application/stream-octet"
      },
  
      data: {
         fileName: fileName
      },
      error: function (err) {
         console.log("ERROR: " + err);
      }
   });

   console.log(request);

   return request;
}