The premium version allow you to insert files of any type (PDF, doc, docx, txt, mp4...) in your notes. There is no limit in the number of attachments. However for optimal syncing performance, each file is capped at 20 MB.
Follow the steps below to insert attachments in your note:
Click the insert button
in the top bar of the note editor and select Insert Fileor use the shortcut Cmd/Ctrl+O
Select the file you want to insert from the Finder/Explorer pop up