Hi Christy,
You can totally store your documents in Method, and even link them to customers, cases, opportunities, solutions, and more! Please see this article which is one of five about Method's Document Library. Through some customization, it is definitely possible to send your documents as attachments. In the Send Email action, there is a field called Attachment Location which can be utilized for this purpose. If you need help setting this up, you can contact an in-house consultants or a Method Solution Providers. Also, here is another post that might shed a bit more information.
If this is something you would like to try and customize yourself, feel free to post more questions on this thread if you get stuck.
Jason