httpbin(1) - HTTP request and response service
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.
Endpoints - View and respond to requests on an HTTP endpoint
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
Beew.io - The simplest way of scheduling HTTP requests.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request