Commerce v1.0 lets you generate PDF Invoices for orders using a PDF Writer. When v1.0 came out we offered an integration with the PDFCrowd service.
Today we've released a new extension that lets you generate PDFs with the mPDF library.
PDFCrowd supports more styling options and is really fast, but requires a monthly subscription. The mPDF library on the other hand is open source and runs on your own server, while still generating good-looking PDFs.
This extension was developed by Murray Wood as an official modmore-supported extension. Thanks, Murray!