We do not limit the size of files that you may upload with your job application. However, your email service provider likely does limit the total size of email messages sent through their server. For example, some email service providers limit the total size of the email to 10 megabytes. This means that the combined size of the job application plus the size of all attachments may not exceed 10 megabytes. The application alone is approximately 50 kilobytes. This limit varies from provider to provider and you must check with your provider for their limits.
If you receive an error when submitting your application that says you have not completed required fields, but you have, you likely have hit the limit of your email provider.