PDFShift is an API that converts any input HTML (raw data or link) to a nice PDF. The service is focused to help developers set up the conversion quickly and focus on their core problem.
Advanced features are available, like watermarking and encryption, and you can see all the available options on the documentation page. The service is free for up to 250 conversions per month. There is a possibility to increase those free conversions by sharing PDFShift on Twitter, writing an article about it or mentioning it on your website. Finally, more conversions can be made with monthly subscriptions ranging from 9$ to 99$.