Add a Dropbox integration like ActiveCampaign has that allows you to embed a link in your email that connects to a file in your Dropbox account. This way users can click a download button in the email and automatically save a PDF or eBook without needing to leave the email and go into Dropbox or Google Drive. https://help.activecampaign.com/hc/en-us/articles/115000183770-Adding-a-Dropbox-file-to-your-campaign