Download true file name instead of from drupal version changed filename
Is all depends on how your loading the file information. As the filename field in the file_managed table will always be whatever is uploaded. e.g.
filename = mypdf.pdf
uri = mypdf_1.pdf

So you can always use the filename value for the real file name. It sounds like whatever you're using to load the file/create the file link isn't using this correct value