You can add a print button/link to the form that the form users may use to print the form they have filled out before submitting it.
Go to the Settings → Advanced section of your form and tick the option Add a Print button on the form, located under Form. A print link will appear on the form when accessed. Form users can use this link to print the form right away.
However, to print digital signatures implies to adjust the browser’s settings so that it can print background images & colors. If you use a digital signature on the form, inform your form users to check these settings in the browser they are using before printing the form.