ASP.NET Framework Returning Large Response

I have an ASP.NET framework web application that processes documents and returns it in a template contract. It works fine for most file, but if the processed file is large, the response is too large to return. This is what we are returning:

public class ControllerBase : ApiController
 {
           .
           .
           .
           .
           protected IHttpActionResult CheckForReport(string guid, 
RepositoryStatus.REQUEST_TYPE requestType, bool returnReport)
 {
                  .
                  .
                  .
                   switch (reportStatus.RequestType)
                   {
                           case RepositoryStatus.REQUEST_TYPE.TagTree:
                               return Ok(Repository.GetTagTree(guid));
                           case RepositoryStatus.REQUEST_TYPE.Metrics:
                               return Ok(Repository.GetMetrics(guid));
                           case RepositoryStatus.REQUEST_TYPE.DocGen:
                                return Ok(Repository.GetReport(guid));
                       }
                 }
     }

Where Repository.GetReport(guid) returns a Document Interface object:

    /// <summary>
 /// The generated document we are sending back to the client.
 /// </summary>
 [DataContract]
 public class Document

Im trying to return the document as a stream, but am struggling to find the appropriate return type for the ApiController class. Any suggestions?

I did this in .NET core, and this is essentially what I ultimately want to be able to do, or some for of this in .net framework

[HttpGet]
        public IActionResult Get()
        {
            string filename = "C:\\WindwardRESTClientSamples\\Windward-RESTful-V2-.NET-Core-Client-Sample\\files\\1gb.docx";
            byte[] bytes = System.IO.File.ReadAllBytes(filename);
            //var dataStream = new MemoryStream(bytes);
            //var temp = new FileResult(dataStream, filename);
            string contentType;
            new FileExtensionContentTypeProvider().TryGetContentType(filename, out contentType);
            contentType = contentType ?? "application/octet-stream";
            return File(bytes, contentType);

UPDATE: NEW CODE ADDED:

 public class FileResult : IHttpActionResult
    {

        private readonly Document genDocument;
        private readonly string contentType;

        public FileResult(Document doc, string contentType = null)
        {
            this.genDocument = doc;
            this.contentType = contentType;
        }

        public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
        {
            return Task.Run(() =>
            {
                var memStream = new MemoryStream(genDocument.Data);
                var response = new HttpResponseMessage(HttpStatusCode.OK)
                {
                    Content = new StreamContent(memStream)
                };

                //var contentType = this.contentType ?? MimeMapping.GetMimeMapping(Path.GetExtension(filePath));
                var tempType = this.contentType ?? "applicatiton/pdf";
                response.Content.Headers.ContentType = new MediaTypeHeaderValue(tempType);

                return response;
            }, cancellationToken);
        }
    }

Then I would return a FileResult object in my controller class:

case RepositoryStatus.REQUEST_TYPE.DocGen:
                        return new FileResult(Repository.GetReport(guid));

I also added these to the web.config file:
< maxRequestLength="2097152" executionTimeout="180"/>

These changes helped slightly, but I still get a out of memory exception thrown.