Found a solution! A well written tutorial here was exactly what I was looking for!

http://umbracodevelopers.sdesign1dev.co.uk/2015/7/30/ajax-newsletter-sign-up/

This may be old, but this is how I solved it:

I created an export button with angular with exportForms as the action

exportForms: function(type) {
            return $http.post("backoffice/MySection/ExportAction/export");
        }

I then built an authorization handler. Just something simple to check if the user was logged in

public class AuthorizationHandler
{
    public static bool UserLoggedIn()
    {
        var httpCtxWrapper = new HttpContextWrapper(HttpContext.Current);
        var umbTicket = httpCtxWrapper.GetUmbracoAuthTicket();
        if (umbTicket == null || umbTicket.Name.IsEmpty() || umbTicket.Expired)
            return false;
        return true;
    }
}

Then I built a surface controller which throws an unauthorized if someone is not logged in.

public class ExportActionsController : SurfaceController
{
    public ActionResult Export(string type)
    {
        if (AuthorizationHandler.UserLoggedIn())
        {
            var query = //my sql statement here
            var forms = DatabaseContext.Database.Fetch<dynamic>(query);

            ExcelService.ExportForm(forms, type);

            if (HttpContext.Request.UrlReferrer != null)
            {
                return Redirect(HttpContext.Request.UrlReferrer.AbsoluteUri);
            }
            return Redirect("/#/MySection");
        }
        else
        {
            throw new HttpException(401, "Unauthorized access");
        }
    }
}

Then I had to handle the exporting. I like to use closedXML.

I'm modifying this code a bit because my original is a bit more complex.

    public class ExcelService
   {
       public static void ExportForm<T>(IEnumerable<T> forms, string filename)
      {
        XLWorkbook wb = new XLWorkbook();

        //this handles exporting my data into a datatable. You have to build this yourself.
        DataTable dt = ToDataTable(forms.ToList());

        //adds a worksheet with the data and the filename is the sheet name
        wb.Worksheets.Add(dt, filename);

        //This handles the download.
        HttpResponse httpResponse = HttpContext.Current.Response;
        httpResponse.Clear();

        //tell it the content type
        httpResponse.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        //give it your filename
        httpResponse.AddHeader("content-disposition", "attachment;filename=\"" + filename + " " + DateTime.Now.ToShortDateString() + ".xlsx\"");

        MemoryStream memoryStream = new MemoryStream();

        //save the workbook as a memory stream
        wb.SaveAs(memoryStream);

        //write file to users computer
        memoryStream.WriteTo(httpResponse.OutputStream);

        //never forget to close the stream and the response
        memoryStream.Close();

        httpResponse.End();
       }
    }

Hope that helps

Thanks Taylor, I'll take a look.

I did get a version working with some AngularJs magic but it's always worth exploring other options!

Thank you @Taylor Mitchell !!

For Umbraco 8 things are a little different, but your reply was a very good starting point.

The button in the html file changes to a simple link:

<umb-button type="link"
    button-style="link"
    label="Scarica PDF"                            
    href="/umbraco/surface/BackofficeDownload/DownloadPDF?ID={{model.dialogData.IDData}}">
</umb-button>

Then the controller changes to:

namespace XXX.Controllers
{
    public class BackofficeDownloadController : SurfaceController
    {
        private readonly ILogger _logger;

        public BackofficeDownloadController()
        {
        }

        public BackofficeDownloadController(ILogger _logger)
        {
            this._logger = _logger;
        }

        [HttpGet]
        public ActionResult DownloadPDF(int ID)
        {
            if (AuthorizationHandler.UserLoggedIn())
            {
                try
                {
                    DocumentGenerator generatore = new DocumentGenerator ();
                    generatore.GeneratePDF(ID);
                    if (Request.UrlReferrer != null)
                    {
                        return new RedirectResult(Request.UrlReferrer.AbsoluteUri);
                    }
                    return new RedirectResult("/#/Preventivi");
                }
                catch (Exception ex)
                {
                    Console.Write(ex.ToString());
                    _logger.Error("Error in BackofficeDownloadController.DownloadPDF", ex);
                    return null;
                }
            }
            else
            {
                throw new HttpException(401, "Unauthorized access");
            }
        }
    }
}

The Authorization Handler remains the same

public class AuthorizationHandler
{
    public static bool UserLoggedIn()
    {
        var httpCtxWrapper = new HttpContextWrapper(HttpContext.Current);
        var umbTicket = httpCtxWrapper.GetUmbracoAuthTicket();
        if (umbTicket == null || umbTicket.Identity == null || umbTicket.Identity.Name.IsEmpty() || !umbTicket.Identity.IsAuthenticated)
            return false;
        return true;
    }
}

Finally the document generator is whatever you need to create the document. In this case I am using ASPOSE.Words to generate a PDF file from a Word Document.

public void GeneratePDF(int ID)
  {
        Document documento;

        try
        {
            MemoryStream stream = new MemoryStream();
            documento = GeneraDocumento(ID);
            documento.Save(stream, SaveFormat.Pdf);
            System.Web.HttpContext.Current.Response.Clear();
            System.Web.HttpContext.Current.Response.Buffer = true;
            System.Web.HttpContext.Current.Response.ContentType = "application/pdf";
            System.Web.HttpContext.Current.Response.AddHeader("content-length", stream.Length.ToString());
            System.Web.HttpContext.Current.Response.AddHeader("content-disposition", string.Format(@"attachment;filename=""Preventivo_{0}.pdf""", IDPreventivo));
            System.Web.HttpContext.Current.Response.BinaryWrite(stream.ToArray());
            System.Web.HttpContext.Current.Response.End();
        }
        catch (Exception ex)
        {
            Umbraco.Web.Composing.Current.Logger.Error(typeof(GeneratoreDocumenti), ex, "Error in DocumentGenerator.GeneratePDF");
        }
    }

I hope it helps to someone else, as the previous answers helped me.

Michele

is working on a reply...