DocRaptor - As the only API powered by the Prince HTML-to-PDF engine, DocRaptor provides the best support for complex PDFs with powerful support for headers, page breaks, page numbers, flexbox, watermarks, accessible PDFs, and much more
neo.tax - automated R&D tax credits for startups = extra month of burn
PDFCrowd - Pdfcrowd is a Web/HTML to PDF online service. Convert HTML to PDF online in the browser or in your PHP, Python, Ruby, .NET, Java apps via the REST API.
Stripe Atlas Taxes - Help file your business taxes
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Quarterly Tax Calculator for Freelancers - See how much you owe to state and federal in 7 sec