You are asking only the SC/ST/PD candidates to enclose the category certificate. What about the OBC (non-creamy layer) candidates? Do they have to enclose the category certificate too?

OBC (non-creamy layer) candidates do not have to enclose the category certificate since their application fee is same as that of the general category candidates. However, in the ONLINE application, you can indicate the category to which you belong to. You need to produce the category certificate only to the admitting institute at the time of admission.