We can add attachments but we strongly advise against it. Attachments are perceived as “malicious”. The best practice is to host your file/attachment on your website or google drive and just include a link to your file in the email.
We can host your file/s in our system. How to upload a document, please follow the steps here: https://help.mailclickconvert.com/faq/how-to-upload-a-document/