As of June 2025, NoteDex DOES support adding audio or file attachments, but recording audio is still in development It is being developed as part of a new Windows beta version. If you are interested please sign up for the windows beta (Mac coming soon): Windows Beta | NoteDex
Also, if you have a hyperlink to the cloud link of the file, you could paste that into the card. e.g. a Dropbox or Google Drive link for instance.