Statement PDFs in Next.js

Why statements become PDFs

A statement summarises a period that is now closed. Regenerating it later from live data would produce a different document, which defeats the point. That is the difference between a document and a view of a database, and it is why finance and account management keep asking for this.

What a statement has to carry

Before any of the code below matters, the template has to produce a document that is actually a statement. These are the fields that make it one, and the ones a reader or an auditor will look for first.

• the opening balance and the closing balance
• every transaction in the period with date, description and signed amount
• a running balance column, so a reader can find where a discrepancy starts
• the account identifier, usually masked
• the statement period, which must not overlap the previous one

Turning your React, rendered to a string on the server template into a document

You already have the markup. RenderToStaticMarkup(<Invoice {...data} />) gives you it as a string, which is the only input the render needs. This is the framework where the incumbent approach fails hardest. A serverless function has a hard bundle size limit, and a Chromium build does not fit inside it. That is why the ecosystem grew a whole genre of stripped Chromium packages, and why an HTTP render is the path of least resistance here rather than an optimisation.

The Next.js implementation

fetch ships with the runtime, so this adds no dependency. The render happens in a Route Handler returning a Response, and you return a Response with the upstream body and a PDF content type.

// app/statements/[id]/pdf/route.ts
import { renderToStaticMarkup } from "react-dom/server";
import { StatementDocument } from "@/documents/statement";
import { documentStyles } from "@/documents/styles";

export async function GET(
  _request: Request,
  { params }: { params: Promise<{ id: string }> },
) {
  const { id } = await params;
  const statement = await getStatement(id);

  // The style tag is the load-bearing part. Your app's CSS lives in a bundle the
  // renderer will never fetch, so the document needs its styles inline.
  const html = `<!doctype html><html><head><meta charset="utf-8">
<style>${documentStyles}</style></head><body>${renderToStaticMarkup(
    <StatementDocument statement={statement} />,
  )}</body></html>`;

  const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${process.env.PDFPIPE_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      html,
      options: { format: "A4", printBackground: true },
    }),
  });

  if (!upstream.ok) {
    return new Response("render failed", { status: 502 });
  }

  return new Response(upstream.body, {
    headers: {
      "Content-Type": "application/pdf",
      "Content-Disposition": `attachment; filename="statement-${id}.pdf"`,
    },
  });
}

The CSS that makes a statement page correctly

The layout problem specific to this document is that a long transaction table spanning many pages, needing repeated headers and a running balance that stays legible after a break. These rules handle it.

/* Line items run past one page. Repeat the header, keep the
   totals block whole, and never strand a single row. */
thead { display: table-header-group; }
tfoot { display: table-footer-group; }
tr    { break-inside: avoid; }

.totals {
  break-inside: avoid;
  break-before: auto;
}

@page {
  size: A4;
  margin: 18mm 16mm 22mm;
}

What goes wrong in Next.js

renderToStaticMarkup gives you markup with no stylesheet attached, because your CSS lives in a bundle the PDF renderer will never load. Inline the styles into a style tag in the string you send, or the document renders with browser defaults.

What people try first

Most Next.js projects reach for puppeteer-core paired with a size-reduced Chromium package, which works but ties your deployment to a binary that has to be rebuilt for every runtime version bump. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.

Where the statement lives afterwards

Rendering is the short part. Statements are the document most often requested again years later, usually for a loan application or an audit. Regenerating one from current data would produce different figures, so the rendered file is the record and has to be stored as issued.

Getting the document right

• Check the closing balance, which has to reconcile with the transactions listed above it.
• Generation is triggered by the end of a billing or accounting period, so size the timeout for that path rather than for a health check.
• This is a batch shape: render the run through the batch endpoint rather than firing thousands of individual requests.
• Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.

Frequently asked

Related

Other Next.js documents, and the same statement in other stacks.