Upload PDF CSOM to Sharepoint Online

using System;
using System.Web.UI;
using Microsoft.SharePoint.Client;
using File = System.IO.File;
using Microsoft.SharePoint;
using System.Security;
using System.IO;
using System.Net;
using Microsoft.Extensions.DependencyModel;
using SP = Microsoft.SharePoint.Client;
using System.Linq;
using System.Web;



public partial class test : Page
{
    public void UploadDocument(string siteURL, string serverRelativeDestinationFilenamePath, string fullLocalFilenamePathToImport)
    {
        using (ClientContext context = new ClientContext(siteURL))
        {
            // Credentials hardcoded here for brevity, in reality you
            // want to store them in a secure location or request user to input them
            string password = "Ox0ypVcVgXXXX";
            string account = "admin@xxx.com";
            var secret = new SecureString();
            foreach (char c in password)
            {
                secret.AppendChar(c);
            }
            context.Credentials = new SP.SharePointOnlineCredentials(account, secret);

            using (FileStream fs = new FileStream(fullLocalFilenamePathToImport, FileMode.OpenOrCreate))
            {
                Microsoft.SharePoint.Client.File.SaveBinaryDirect(context, serverRelativeDestinationFilenamePath, fs, true);
            }
            var newFile = context.Web.GetFileByServerRelativeUrl(serverRelativeDestinationFilenamePath);

            context.Load(newFile);
            context.ExecuteQuery();

            //check out to make sure not to create multiple versions
            newFile.CheckOut();

            var item = newFile.ListItemAllFields;

            // update some metadata if you need to, for example:
            // item["Title"] = "My Uploaded File";
            // item["CustomFieldName"] = "Some Custom Value";
            // item.Update();
            // context.ExecuteQuery();      

            // use OverwriteCheckIn type to make sure not to create multiple versions 
            newFile.CheckIn(string.Empty, CheckinType.OverwriteCheckIn);
        }
    }
    protected void Page_Load(object sender, EventArgs e)

	{
    
        UploadDocument("https://xxxx.sharepoint.com", "/test/document.pdf", @"h:\document.pdf");
    }
}