pdf-lib-bulk

Bulk PDF generation for pdf-lib — without re-parsing your font for every single document.

pdf-lib calls fontkit.create(bytes) inside every embedFont(). Generate 100,000 invoices and you parse the same TTF 100,000 times. This library amortizes that away:

| Workload (100 one-page PDFs, custom TTF, Apple M1) | pdf-lib naive | pdf-lib-bulk | Speedup | | --- | --- | --- | --- | | Variable text per document (bulkGenerate) | 1,399 ms | 347 ms | 4.0x | | Identical documents (makeTemplateCloner) | 1,515 ms | 48 ms | 31x |

Reproduce with bun run bench/bench.ts.

Install

npm install @libs-jd/pdf-lib-bulk pdf-lib @pdf-lib/fontkit

Usage

Variable content per document (invoices, letters, tickets)

import fontkit from "@pdf-lib/fontkit";
import { bulkGenerate } from "@libs-jd/pdf-lib-bulk";

const fontBytes = await fs.promises.readFile("Inter-Regular.ttf");

const pdfs = await bulkGenerate(invoices, {
  fontkit,                       // parsed once, reused for every document
  fonts: { body: fontBytes },
  draw({ doc, fonts, item }) {
    const page = doc.addPage();
    page.drawText(`Invoice #${item.id} — ${item.total}`, {
      x: 50, y: 700, size: 24, font: fonts.body,
    });
  },
});
// pdfs: Uint8Array[] — one standalone PDF per invoice

Identical documents (certificates, blank forms)

import { makeTemplateCloner } from "@libs-jd/pdf-lib-bulk";

// build the document once, however you like (fonts embedded once, layout once)
const templateBytes = await buildCertificateTemplate();

const cloner = await makeTemplateCloner(templateBytes);
const pdfs = await cloner.cloneMany(10_000);

Just the font cache

If you want to keep your own generation loop, wrap fontkit yourself:

import fontkit from "@pdf-lib/fontkit";
import { cachingFontkit } from "@libs-jd/pdf-lib-bulk";

const fk = cachingFontkit(fontkit);
// ...
doc.registerFontkit(fk);                     // same API, parse happens once
const font = await doc.embedFont(fontBytes, { subset: true });

How it works

• cachingFontkit — memoizes fontkit.create() per font buffer (WeakMap keyed by the Uint8Array you pass), so the expensive TTF/OTF parse happens once per font instead of once per document. Fonts are still embedded and subset per document, so every output PDF is standalone.
• bulkGenerate — a generation loop with the cache pre-wired: create doc → embed cached fonts → your draw callback → save.
• makeTemplateCloner — loads your finished template once and produces copies via copyPages, skipping layout, font parsing, and font embedding entirely.

About

Contributions welcome — please open an issue or PR. If this saved your batch job some hours, a ⭐ helps others find it.

Related

• pdf-lib — the PDF library this builds on
• @libs-jd/xlsx-parse-table — parse tables from Excel worksheets

Author

Jeet Dhandha — GitHub

License

MIT