The issue is how to hide file attachments in Read Mode and display them during Edit Mode on the web. Any attachments
added using the File Upload control will be associated with the first Rich Text Field displayed on the web (with the option, Using Java Applet).
If this contains other data, you will not be able to hide the files without hiding the entire contents of the field.
Create an additional Rich Text field on the form (above all other rich text fields) and ensure you set it to Using Java Applet. Hide the field in Read Mode using normal hide with formulas.
To ensure the field exists and can be written to by the File Upload control (but is not available to end users for modification), set the HTML Attributes to "height=0; width=0." This hides the empty field (except file attachments).