Timy - Best way to send scheduled messages in Slack
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Slater by Convergely - Schedule your Slack messages now, post them later
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
SKEDit Scheduling App - SKEDit Scheduling App is a rich-featured scheduling application that entitles you to automate your messages by scheduling your WhatsApp messages, SMS, e-mails, post, and set call reminders to experience a healthy or tension-free lifestyle.
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.