You can attach two kinds of submission PDFs to outgoing emails. The first is a default summary that is available on all plans, which cannot be modified. The second kind is a Custom PDF, which can be created under "After Submission → Custom PDFs" on Pro and Agency plans.

To attach either kind of PDF summary, simply select it from the "Attach Custom PDFs" dropdown when setting up a custom email.

Screenshot of a custom email configuration, with the "Attach Custom PDFs" dropdown highlighted (toward the bottom)

In either case, the PDFs listed here are dynamic documents that are generated on form submission. If you'd like to attach a static PDF (that will be the same for each submission), you can use the "ADD ATTACHMENT" button instead and upload the file directly from your computer.