What is the largest document I can attach to a form?

I have a form that could have a 15MB .pdf file that I want to upload.

The maximum file upload size can be increased.  Here is our quick guide detailing how to increase the limit as well as the maximum file sizes for different integrations:

https://www.jotform.com/help/33-Changing-the-Upload-Size-Limit

You can also change the allowed file types:

https://www.jotform.com/help/29-Upload-Field-Allowed-File-Types