UnityPDF - UnityPDF lets you merge, split, divide, rotate, protect PDF files and more.
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
PDFsam - PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Clipperly - Convert, edit or optimize your files online. More than 400 different formats supported among documents, images, spreadsheets, ebooks, archives, presentations, audios and videos.
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.