How do I create a .pdf file efficiently from an HTML template in Rails?

There are options like prawn, but they rely on a specific DSL. I am guessing you would like to print a pdf version of an existing view. I would recommend looking into pdfkit. We have used it in the past, and although it has some issues, it works quite well. https://github.com/jdpace/PDFKit/

You could also try http://docraptor.com. It works on a freemium model and is easy to use.

Use an API like http://www.htm2pdf.co.uk/html-to-pdf-api - code samples in Ruby included.

Try the http://www.web2pdfconvert.com/, which could convert the online webpage into PDF format and send to you via Email. What you need to do is just input the URL and click Convert.

I've found that proper usage of media queries for browser printing is the most effective. If you can't get the result you want: PDF Prawn is a good gem for rendering your data to PDF. I've tried a lot of pdf converters but they just tend to do a mediocre job. They also are a hassle. PDF has restrictions, so when I go to PDF I tend to rethink and ask 'what do these people really want to see in print'? People looking to print are typically looking for something very specific. Typically custom reports or charts will end up a better and efficient way to meet requirements.

If you want to use existing PDF as template, defining areas (bounds, name, type, ...) to be filled later (e.g. with values from Web form), you can use Dhek template editor. Created template is saved in open format (JSON), so it can be processed in any language (PHP, Python, Ruby, Java, .Net): https://github.com/applicius/dhek .