I went ahead and got onto the chat to see and according to them you have to set the attachment links through the PDF. So I guess that means what we're doing, i.e. going back in and putting new attachments on top of the disabled icons, is really the only way to do that right now. If someone else comes across this post and understands what I'm trying to do and knows a way that the help center didn't understand, feel free to post.
Thanks!