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
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.
CloudConvert - convert anything to anything - more than 200 different audio, video, document, ebook, archive, image, spreadsheet and presentation formats supported.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
wkhtmltopdf - wkhtmltopdf is an open source (LGPL) command line tools to render HTML into PDF and various image...
Tcpdf - TCPDF: Open Source PHP Class for generating PDF documents