generates uppercase fields

Can you elaborate more on this?

I assume you want to change case in the filled PDF file.

It is not easy to do, but you can write some JS or PHP to do this for you.

See this discussion: https://stackoverflow.com/questions/47805338/contact-form-7-change-subject-to-uppercase

This can be used as well: https://ww.wp.xz.cn/plugins/contact-form-7-dynamic-text-extension/