Doodle for Messenger - Doodle Anything and Send it on Facebook Messenger
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.
ScribbleBoard - iOS8 Keyboard for hand drawing your messages
Doczilla - Effortlessly create stunning PDFs and screenshots. Seamlessly store them in your own AWS or Google Cloud Storage bucket, putting the control and creativity right at your fingertips.
Anvil PDF Filling API - The easiest way to programmatically populate any PDF
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