Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
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
Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
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.
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request