I'm creating a custom vendor bill approval workflow. Once the Bill is submitted for approval, I have a "Send Email" action which emails a nice message to the next approver, with the vendor bill attached (Actually it shows underneath the message, inline below as per my screenshot). However, this only sends the standard HTML version, as opposed to the advanced PDF version that looks prettier and I also customised by adding a field custom fields. I have set the custom Adv PDF as preferred, but that didnt not work. What am I missing here?

Kinda surprised you can even send the bills that way - I didn't think those were printable

What form is it using? You have to specify the email template on the form.

@KevinJ of Kansas Yes I was surprised too, but it worked!