How to send secure email attachments

Refer http://office.microsoft.com/en-us/outlook-help/encrypt-e-mail-messages-HP001230536.aspx

You can ecrypt these files , after encryption then you can pack these files in winrar program by setting strong password. I think is enough to secure these file. If some one get that rar file 1st he need to break the password which is very difficult for above 15 chracters and file inside the rar also encrypted.

you can see couple of software to encrypt pdf and doc by googling
1. http://www.verypdf.com/encryptpdf/encrypt-pdf.htm
2. http://www.pdfmachine.com/genp/overview.html?ref=GA&campaign=features&adgroup=features&ad=001&gclid=CKO929Hm3K4CFUp66wodNRtAYw
3. http://www.askdavetaylor.com/how_to_encrypt_pdf_file_mac_windows.html

for doc
http://www.oraxcel.com/projects/encoffice/help/encrypted_documents.html
http://www.lucion.com/terminology-doc-file-encryption.html

winrar
http://www.rarlab.com/

After ecrypted files packed in rar file then you can send rar file.

Simplest (but quite definitely NOT the cheapest) is to install a cisco ironport device.
http://www.ironport.com/securedemo/

The Ironport is a smtp filter device that sits between your mailserver and the internet. outbound mail (selectively if you wish) is encrypted, and sent to the recipient, who must then register at the cisco CRES site to decrypt their mail.

from your point of view, all you need to do is either specify that certain messages (eg, messages with attachments to a list of domains) are always encrypted, that certain flags (eg setting "confidential" on an email) triggers the encryption, or anything else you want - the ironport is quite flexible in what will cause the outbound mail to be encrypted. as a bonus, replies to encrypted messages are themselves encrypted, without the recipient needing to buy or set up anything other than the cres login.

Thanks - this is for sending confidential legal reports via email. Obviously this can't be done over regular email as it's not secure enough. As it's for a freelancer I think the Cisco Ironport route is going to be way too expensive - but thanks anyway.

I'm thinking using a strong password in Adobe Acrobat to encrypt the document then sending it as an attachment is probably the way to go as these reports go to many different legal people all using different systems. We're just waiting on a response from the legal IT people to see if this is secure enough.