I have SharePoint designer workflow, one of action is sending email!
How can I send a PDF file as attachment not as a link in email action?
The whole premis of SharePoint is not to distribute documents around the organisation using mail, as such it is not possible to send a mail with an attachment. The best you can do out of the box is to send a link to the document - otherwise you would need to either use a 3rd party solution or go by some form of powershell script.
I'm not sure you can do that, but there are third-party tools to help you. Check this short video: Send email with attachment to external users using workflow in SharePoint 2013 or Office 365