How can I insert an attached file in my form?

Is necessary any plugin? 

Thank you for the support and excellent site,

Valdir Vaz

Do yo want to include attachment in the email of your form? If it is, please refer to the user guide below.

https://www.jotform.com/help/393-How-to-Attach-a-File-to-Autoresponder-Emails

It is also possible to upload files using your form.

User guide: https://www.jotform.com/help/332-How-to-Create-File-Upload-Forms

Let us know if you need further assistance.