To give you some pointers you would have to upload the document first as the web server have no access to the local machine to be able to pick it up.
Then you need to attach it to the email and send it.
Now you need to clear down the uploaded file.
To upload a file http://www.tizag.com/phpT/fileupload.php
To send the attachment http://www.webcheatsheet.com/php/send_email_text_html_attachment.php
Hope this helps