Sure, this is a form of e-invoicing. Just not a very good one. First of all, it’s possible for hackers to intercept and even clone your emailed invoices, inserting their bank details, tricking your customers into paying them instead.
Secondly, you have no visibility of who has opened, read and acknowledged invoices sent in this way.
Thirdly, PDF attachments to emails get stopped by a lot of spam filters. Your invoices might not even reach all of your customers, preventing them paying outstanding invoices by the due date and resulting in late fees for your customers.
The best e-invoicing is done via an EIPP platform, such as Corcentric EIPP, to ensure you benefit from security, visibility, automation, formatting, delivery and payment handling that is not possible when simply sending e-invoices as PDFs over email.