Exception in 2/files/download: "unsupported_file"

We are trying read content of paper file, getting below exception

com.dropbox.core.v2.files.DownloadErrorException: Exception in 2/files/download: "unsupported_file"
at com.dropbox.core.v2.files.DbxUserFilesRequests.download(DbxUserFilesRequests.java:1278)
at com.dropbox.core.v2.files.DbxUserFilesRequests.download(DbxUserFilesRequests.java:1297)
at com.amazonaws.kendra.connector.dropbox.model.item.PocInputStreamToString.main(PocInputStreamToString.java:36)

 

Below is code we are using 

 

DbxDownloader dbxDownloader= client.files().download("/First Paper.paper");
  // Metadata metadata=client.files().getMetadata("/document.docx");
    InputStream inputStream= dbxDownloader.getInputStream();
   DataInputStream dataInputStream = new DataInputStream(inputStream);
   String tmp;
   StringBuilder inputLine=new StringBuilder();
    while ((tmp = dataInputStream.readLine()) != null) {
        inputLine.append(tmp);
        //System.out.println(tmp);
    }

   System.out.println("File content--->"+inputLine.toString());