iTextSharp not working in IE x64 - asp.net

Question

I just transitioned my ASP.NET MVC project from Spire.PDF to iTextSharp (due to the limitations in the free version of Spire.PDF). However I cannot get even the simplest example to work correctly for some reason.
What happens is that the browser (IE 11 x64 in this case) will just display an empty grey page. If I keep this page open for a while then Adobe Acrobat displays an error message (103:103).
The interesting part is that when I save the file (either by adding a Content-Disposition header or by using Fiddler) then the PDF opens without problems. I also found out that Edge and the 32 Bit version of IE will display the PDF file just fine.
Here is my sample Action method:
public ActionResult DownloadPdf() {
var document = new Document(PageSize.A4, 50, 50, 25, 25);
var output = new MemoryStream();
var write = PdfWriter.GetInstance(document, output);
var titleFont = FontFactory.GetFont("Arial", 18, Font.BOLD);
document.Open();
document.Add(new Paragraph("Test Receipt", titleFont));
document.Close();
Response.ContentType = "application/pdf";
Response.BinaryWrite(output.ToArray());
return new EmptyResult();
}
This is what the result looks like: https://onedrive.live.com/redir?resid=17E4A59AD907D9BA!259495&authkey=!ABsQUl-TiR668xI&ithint=folder%2cpng
Any ideas other than setting Content-Length or Response.Buffer? (I tried those already)
Update 1: I'd like to reply to some of the comments
#ChrisHaas even after changing the content type, IE would still display the grey page. However, I used Fiddler to save the response (once with header and once without) in the OneDrive link which you can find in my question above.
#Matt do you mean F12 dev tools? It won't load up correctly on the grey page, it's just a blank white area. So I can't really inspect anything.
#Paulo I tried this before and it didn't have any effect. However the Content-Length seems to be correct anyway according to Fiddler.

Answer 1

I still don't understand what exactly the problem is but I decided to test this on a different PC and determine whether it is a server-side or client-side problem.
I reconfigured IIS Express to allow remote connections and accessed the PDF file from another system (also Win 10 Pro x64 with IE 11) and it worked perfectly. It also behaved correctly depending on the content-type (i.e. download dialog for octet-stream and inline PDF viewer for application/pdf).
Next thing I did was reinstall Adobe Acrobat Reader DC on my dev machine but the problem was still there, even after rebooting and clearing the IE cache. So the last thing I tried was downgrading from version DC to X - this actually worked and will now display PDFs in the browser normally.
Like I said, I don't understand exactly what the problem was but at least I can continue working on my project now.
Thanks everyone for the suggestions though!