I don't give feedback of this sort too often, so this might not necessarily be useful. Now, for the actual feedback. This is a very useful product to have for

I don't give feedback of this sort too often, so this might not necessarily be useful. Now, for the actual feedback. This is a very useful product to have for the intended target audience. From looking at the landing page, your target audience is developers who need to generate PDFs directly from a template. This is only useful if they need PDFs in bulk, if not they can export to PDF. While developers are a good target market, there is also the market of all people who need to generate PDF reports in bulk. You could add a simple frontend allowing anyone to upload a template, with a spreadsheet containing the values to substitute. Think of the spreadsheet as the API parameters. Non-developers can easily use this interface and are very likely to find this service very useful. In addition, you can charge more since the interface will not require any dev skills to use. The catch with this approach though, is that it might be harder to scale. When targeting enterprises a single sale gives you more revenue. All the best!