How to add a new attachment field in supplier quotation form in supplier portal?

I have requirement that when supplier is sending his quotations, optionally he can attach the docx/pdf file.
As supplier portal is not within the desk, I am unable to find the doctype/customize form for that. So I am unable to add field from the customize form.

Please guide me how can I enable attach field in supplier portal. If it is not possible from the desk, guide me on steps for how to write the source code in rfq.html and rfq.js.

Hello @Radha_Krishna - Did you ever find a solution to this? It is an important feature that we want in our implementation.

Hi, any solution for this thread?