It is not possible to send email attachments. The systems we use (our own, as well as those of actual mail senders) are designed for mass mailing. File attachments would increase the volume of data many times over for hundreds of thousands of e-mails. This costs time and money. In addition, the probability increases that an e-mail with an attachment will be blocked by the recipient's server (e.g. because of suspected spam).
Please use a download link to send the recipients your PDF, for example. For example, you could upload your document to the free Google Drive (if you have a Google account) or use Dropbox. This way you can get even more information about the recipient, e.g. when the file was opened, where the recipient is located, what kind of device and what kind of browser the link was opened with, etc.