We do not support direct attachment to emails.
Seriously? Why not?
When you attach a file to an email:
you won't be able to track who clicked on it
your email is more likely to get flagged as spam by Internet Service Providers (or even by the subscribers) because of the risk of attachment-based email viruses
you have to deal with much slower deliverability times, while the attachment can increase the size of your message
your emails are more likely to get bounced due to mailbox storage and file size limits
Overall this may harm your sender reputation (included deliverability rate and domain identity).
We know there are better ways to investigate this while keeping your rates at a high level and gaining insight.
Most popular ones:
Host the file using a 3rd party platform (such as Dropbox, GDrive) then link to that file from your email.
Add a file by hosting it on your website then just share the link with your subscribers.