Can a "upload a file" link be added to a JotForm?

Yes, you can add a file upload field to your form to allow users to upload files along with their

submission data.  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