We've made some improvements to the Preview tab for HTML templates.
We previously rendered the preview HTML/CSS directly in your browser, but there were often some differences between the browser preview and the actual PDFs that were generated. This was especially annoying for headers, footers, margins, and page breaks.
We now use the same PDF rendering engine to generate real preview PDFs with random data. These are rendered using your browser's PDF viewer:
Our HTML template previews are now 100% identical to the actual PDFs that you generate via API requests or by filling out the online form. Headers, footers, and margins can still be quite tricky to get right, but this faster feedback loop should make things much easier!