As of now, it doesn't seem to be possible to attach a file to a booking.
For example:
It'd be useful if a customer could fill a form when booking an appointment and then be able to retrieve the filled form in PDF attached to the booking.
For now, we managed to insert a Zoho Form web link in the booking description. When the form is filled, it's attached to the contact in Zoho CRM which is connected to Zoho Bookings. Clearly, this is not optimal!
Thank you