I mistakenly sent a huge document to my jotform account. How do I delete forms and uploads that I do not want?

You need to delete the submission with the huge attachment document. To do that, please follow this guide: https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data

Keep in mind that deleted submissions are not recoverable. 

I hope this information helps. Thank you.