Guides / C#
Invoices, contracts, reports, certificates: every product eventually needs PDFs, and C# PDF libraries make you hand-position every box. RasterKit prints through real Chromium instead — write ordinary HTML and CSS, POST it, get a finished PDF back.
Because it's a print pipeline rather than a drawing API, you keep your existing templates and stylesheets: flexbox, grid, web fonts, page-break CSS, repeating headers and footers with page numbers all just work.
Sign up free (magic link, no card) — your key is shown right after sign-in. You get 100 renders/month free across screenshots, PDFs, and images.
using System.Text;
var client = new HttpClient { Timeout = TimeSpan.FromSeconds(60) };
client.DefaultRequestHeaders.Add("x-api-key",
Environment.GetEnvironmentVariable("RASTERKIT_API_KEY"));
var body = new StringContent(
"""{"url": "https://example.com/invoice/42", "format": "A4", "print_background": true}""",
Encoding.UTF8, "application/json");
var res = await client.PostAsync("https://rasterkit.com/v1/pdf", body);
var bytes = await res.Content.ReadAsByteArrayAsync();
if (!res.IsSuccessStatusCode)
throw new Exception($"Render failed: {(int)res.StatusCode} {Encoding.UTF8.GetString(bytes)}");
await File.WriteAllBytesAsync("document.pdf", bytes);
Console.WriteLine("Saved document.pdf");The response body is the file itself — no JSON envelope to unwrap, no second download request. Errors come back as JSON with a stable error code.
The PDF API reference documents every parameter. The ones people reach for first:
format: "Letter", landscape: true — paper setupfooter_template — page numbers via <span class="pageNumber">print_background: true — keep your CSS backgrounds (on by default)wait_for_selector — wait for charts/data before printingPass footer_template with Chromium's built-in classes, e.g. <span class="pageNumber"></span> / <span class="totalPages"></span>.
Browsers skip backgrounds when printing by default. RasterKit sets print_background: true by default — if you turned it off, turn it back on.
Yes — standard CSS (break-inside: avoid, break-after: page) is respected, and prefer_css_page_size lets your @page rules define the paper size.