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
Grammarly - Clear, effective, mistake-free writing everywhere you type.
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.
GrammarChecker.net - Grammar Checker is an online spell check tool. It effectively works on English sentence correction, Punctuation mistakes of 28 other different languages.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.