Hi I have the same question as well. Looked at printboss and found it rather clunky. Would prefer a solution that is smoother (meaning the invoice number is automatically added to the email without going through additional hoops).

Raised it in a wishlist - but I guess the demand is not critical enough. Perhaps if more users chimed in...

Thanks for reading !

There may be multiple invoices included in an invoice print / email - this would preclude referencing one invoice number.  
There really should be some refinement added in the ability to easily manage printing of invoices, statements, PO's etc.

There may be multiple invoices included in an invoice print / email - this would preclude referencing one invoice number.  
There really should be some refinement added in the ability to easily manage printing of invoices, statements, PO's etc.

This is correct.  As you can email several invoices with one email, it wouldn't be possible to create a variable.. the invoice forms are attached to the email and contains the invoice numbers but requires the client to open the attachments.  As others have said in this thread, Print Boss has the ability to do this.