You can add up to 2 default attachments (your terms and conditions, for example) to the emails you send with LSP.expert. For that, you have to go to Settings > Document and email configuration. You select the document configuration concerned, and you click on the Emails tab.
For each document, you can add up to 2 attachments by clicking on the 'Upload an attachment' link:
These documents will be automatically attached to all the emails you send using LSP.expert (to the clients for whom you selected this document configuration).