See if you see the official information available, there are no mentions of the document to be issued by the state government of Karnataka. So you can produce official documents issued by some other state administrative authority and certainly it will not create problems. If there are such criterions then the official brochure or any other sources in the official website would have contained the same.

To know more about KCET counselling visit the link below:

https://engineering.careers360.com/articles/kcet-counselling

I hope this answer helps. All the very best for your future endeavors!