WebMerge - WebMerge is an online platform that allows you to easily collect data, populate a document and send it to any contact automatically.

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.

docassemble - docassemble is a free, open-source expert system for guided interviews and document assembly.

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

HotDocs - Template-driven, automated document & form assembly software

PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request