You can’t send attachments in campaign emails or journeys due to the fact that attachments are more likely to be caught in spam filters, as well as the fact that they can significantly slow down campaign send times. You can, however, send PDF attachments of up to 25MB in transactional emails, such as PDF receipts and invoices. If you need to share a file from your campaign emails you can do this by hosting the file online and including a link to the file within the email.