I'm getting the same problem and I believe this is good workaround. I have DNN 4.3.4, and when I add a link using the 'Create Link' button in the Rich Text Editor, it creates the following HTML for the link:
<A href="http://www.myurl.comPortals0document.pdf">click here</A>

I modified this to read:
<A href="http://www.myurl.com/Portals/0/document.pdf">click here</A>

This seems to work for me now.

Regards,
Bryan

The thinking at present is that the problems are caused by the wrong content-type, combined with no content-length header.  And for some users experiencing the PDF issue, it actually *is* the PDF viewer bug...  So the change you posted about in the linked post is one of two changes to deal with this issue.

If you are making core changes to DNN, you should probably wait for 4.3.5 (or even 4.3.6), as these will contain changes to improve stability and performance.  And (of course) it's best to make your changes in such a way as to not require a change to the core...