9. Files and Folders ↑
9.4 File Links
You may use a Link field to store a link to a local file or folder.
Such a link would start with file:// and would contain a complete path to the file or folder.
You may use the Set Local Link command, beneath the Note menu, to select a file or folder to be linked using the Link field.
You may also drag a file (other than a text file) from the Finder to the List tab of a Collection, and then drop it after an existing row (but not on it), in order to create a new Note pointing to the dragged file, with a Title based on the name of the file.
If you would rather have such a file stored as an attachment, you could then use the Convert Local Link to Attachment command – again beneath the Note menu – to convert the file link to a File Attachment.