By default, Drupal does not support allowing a user to upload a file in a webform which can then be sent as an email attachment. Drupal can accomplish this using the contributed modules Webform and Swift Mailer.
The Webform module is a comprehensive module that allows you to create and configure webforms. In a nutshell, it will enable you to create a webform with many variations of form fields. After submission, the results can be sent via customizable emails.
This tutorial will focus on creating a file upload field whereby a user can upload a local file into a webform.