Hi Annette,
Sorry but no, there is not and it is not currently a planned improvement. I suggest just link to the file from the newsletter with a normal link.
It is not likely that we will ever add support for attachments in the newsletter. In my opinion that would be very unconventional and would likely result in more blocking by spam filters if the newsletter had any attachments. I don't recall ever receiving a newsletter with an attachment.
Best,
Joe