I have leads & accounts who use a product. I'd like to send a email about updates. Now what?

I have leads & accounts who use a product. I'd like to send a email about updates. Now what?

I created a product. 
I linked certain Accounts and Leads to this product.
I have a new document about product updates.

What is the most efficient way to get this document out...Do i have to create an email template (separate for leads and accounts)?
Why can i not send an email direct from product page?