Have you considered offering this as a browser extension? It would greatly increase your market size, and I have worked with (non-technical) people who would love to be able to activate an extension, enter an email address, and email out a PDF (of an invoice) to a colleague.

This workflow is a common one, and really frustrating: "Print -> Save as PDF -> choose location on disk/google drive/dropbox-> Save -> switch to email -> compose email -> enter email address -> enter subject -> add attachment -> navigate to saved location (if I can remember it) -> Send".

You could even add a premium feature that would hit a URL on a schedule, to automate report sending to managers (e.g. of Yahoo Ads or any other platform with similarly terrible reporting).

My manager and I at my old place of work used to spend 1-3 hours/month, times however many people had access to his credit card for their subscriptions.