Tcpdf - TCPDF: Open Source PHP Class for generating PDF documents
pdflayer - Free, powerful HTML to PDF API supporting both URL and raw HTML conversion. Unlimited document size, lightning-fast and compatible PHP, Python, Ruby, etc.
HTML2PDF.fr - HTML2PDF is a HTML to PDF converter that allows the conversion of valid HTML 4.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
PDF-LIB - Create and modify PDF documents in any JavaScript environment
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