Skim - Skim is a PDF reader and note-taker for OS X.
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.
Zhizhi Reader - Zhizhi Reader is a web-based software that helps you to read documents and books easily.
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
Xodo - Try easy-to-use PDF tools that keep your documents safe. Work with your important files across all platforms and devices with the ultimate all-in-one document solution. Your productivity lives at Xodo!
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request