Can a user (filling out the form) attach a document(s)?

I would like to know whether we can ask users that are filling out a form, to attach a document or two, to their submission?  If so, can you please provide details on how to build this in to a form?

Yes, you can allow your users to upload files when completed your online form. Here's a guide on how to add a file upload on your form: https://www.jotform.com/help/332-How-to-create-upload-forms 

If you wish to make the file uploads as an attachment on your email alerts, then you can check this blog post, a new feature was just released for that functionality: https://www.jotform.com/blog/223-New-Feature-Get-Uploaded-Files-as-Email-Attachments 

I hope that helps.