browserling - Live interactive cross-browser testing from your browser.
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
BrowserStack - BrowserStack is a software testing platform for developers to comprehensively test websites and mobile applications for quality.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Browsershots - Browsershots makes screenshots of your web design in different browsers.
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.