in magento there is no available methods for attach file. once we do it in magento by adding a following code
in  mage/core/model/email/template.php at the end of file.

public function addAttachment(Zend_Pdf $pdf){
        $file = $pdf->render();
        $attachment = $this->getMail()->createAttachment($file);
        $attachment->type = 'application/pdf';
    $attachment->filename = 'yourfile.pdf';
    }
   
but i prefer to use Zend_Mail to send mail with attached file.
for this u need to do following.

try{
            $mail = new Zend_Mail();
            $mail->setFrom("fromemail","fromname");
            $mail->addTo("toemail","toname");
            $mail->setSubject("subject");
            $mail->setBodyHtml(" body text"); // here u also use setBodyText options.
       
            // this is for to set the file format
            $at = new Zend_Mime_Part($content);
           
            $at->type        = 'application/csv'; // if u have PDF then it would like -> 'application/pdf'
            $at->disposition = Zend_Mime::DISPOSITION_INLINE;
            $at->encoding    = Zend_Mime::ENCODING_8BIT;
            $at->filename    = $filename;
            $mail->addAttachment($at);
            $mail->send();
  
        }catch(Exception $e)
        {
            echo $e->getMassage();
           
        }

http://mehtagaurav.blogspot.com/2010/08/send-mail-with-attached-file.html

send mail with attached file
examples: http://framework.zend.com/svn/framework/standard/trunk/tests/Zend/Mail/MailTest.php

Magento Send email easily using Zend_Mail with attached file

email, magento

PHP