Boxpdf

boxpdf

A box-layout DSL over pdf-lib. Runs in Node 18+, Cloudflare Workers, Deno, and browsers. No native dependencies, no WASM, no headless browser.

Live gallery: https://earonesty.github.io/boxpdf/

import { cleanTheme, flowToPdf, hline, hstack, standardFonts, text, vstack } from "boxpdf";

const bytes = await flowToPdf(async (pdf) => {
  const { font, bold } = await standardFonts(pdf);
  const theme = cleanTheme({ font, bold });

  return [
    vstack({ gap: 8 },
      text("Receipt #18472", theme.type.h1),
      text("May 14, 2026", theme.type.caption)
    ),
    hline(theme.hr),
    hstack({ gap: 16, justify: "between", width: 515 },
      text("Wool socks", theme.type.body),
      text("$28.00", { ...theme.type.body, font: bold, align: "right", width: 80 })
    )
  ];
});

No pdf-lib import, no manual PDFDocument.create() / pdf.save() bookkeeping. flowToPdf owns the document lifecycle and returns the bytes; standardFonts embeds the built-in Helvetica family (regular, bold, italic, bold-italic) in one call.

import { PDFDocument, StandardFonts } from "pdf-lib";
import { cleanTheme, renderFlow, text, vstack } from "boxpdf";

const pdf  = await PDFDocument.create();
const font = await pdf.embedFont(StandardFonts.Helvetica);
const bold = await pdf.embedFont(StandardFonts.HelveticaBold);
const theme = cleanTheme(font, bold);

await renderFlow(pdf, [
  vstack({ gap: 8 },
    text("Receipt #18472", theme.type.h1),
    text("May 14, 2026", theme.type.caption)
  )
]);

const bytes = await pdf.save();

Install

npm install boxpdf pdf-lib

pdf-lib is a peer dependency.

What it does

• Declarative layout primitives: vstack, hstack, text, image, hline, vline, spacer, flex, keepTogether, link, svgPath, table.
• Padding, margin, background, background images, borders, borderRadius, overflow clipping, flex-grow, flex-shrink, justify, align.
• Rich paragraphs with mixed inline runs, inline replaced nodes, hard breaks, hanging indents, and optional paragraph floats.
• Word wrapping with maxLines truncation, optional breakWords, and no-wrap control.
• Themes: cleanTheme, stripeTheme, editorialTheme, brutalistTheme.
• Multi-page flow with per-page headers and footers, stack fragmentation, and table row fragmentation.
• Streaming generation for memory-bounded output.
• PDF link annotations, text decorations, document metadata.
• ~7 KB minified core. Custom fonts pull in @pdf-lib/fontkit only when you call loadFont or embedInter.

Templates

Files in templates/ cover receipts, boarding passes, resumes, order confirmations, and certificates. Each is a single file.

Scaffold one into your app with the CLI:

npx boxpdf init receipt --out src/pdf/receipt.ts
npx boxpdf list

The CLI also ships a resource-only MCP server for agents:

claude mcp add boxpdf -- npx -y boxpdf mcp

Themes

import { cleanTheme, editorialTheme, standardFonts } from "boxpdf";

const theme = cleanTheme(await standardFonts(pdf));            // Helvetica
const serif = editorialTheme(await standardFonts(pdf, "times")); // serif + italic slot

Every theme factory accepts either a { font, bold, italic? } object — which is exactly what standardFonts(pdf) and embedInter(pdf) return — or the legacy positional fonts:

cleanTheme({ font, bold })            // or cleanTheme(font, bold)
stripeTheme({ font, bold })
editorialTheme({ font, bold, italic }) // or editorialTheme(font, bold, italic)
brutalistTheme({ font, bold })         // courier regular + bold

standardFonts(pdf, family) takes "helvetica" (default), "times", or "courier" and returns { font, bold, italic, boldItalic }. Every theme exposes the same shape: colors, spacing, radii, type, card, hr.

API

Containers

• vstack(style, ...children). Vertical layout.
• hstack(style, ...children). Horizontal layout.
• keepTogether({ gap?, margin? }, ...children). Paginates atomically.

Container style:

Leaves

• text(content, { size, font, color?, align?, width?, lineHeight?, maxLines?, underline?, strikethrough?, margin? }). Word-wraps when width is set. Truncates with ellipsis when maxLines is set. Default lineHeight uses the font's full height, including descenders.
• paragraph({ width?, align?, lineHeight?, margin?, paddingLeft?, textIndent?, wrap?, floats? }, ...runs). Mixed inline text runs and atomic inline nodes that wrap together as one paragraph. Use run(text, style), linkRun(text, style, href), and inlineNode(node, { verticalAlign?, href? }). Newlines in runs create hard breaks; wrap: false disables soft wrapping.
• image(pdfImage, { width, height, margin? }). Takes an already-embedded PDFImage.
• imageFit(pdfImage, { width, height, fit?, margin? }). Draws an image centered in a fixed rectangle, scaled to contain (default) or cover with clipping.
• spacer(size, { grow? }) / flex(weight = 1). Fixed or growing gap.
• hline({ color, thickness?, width?, margin? }).
• vline({ color, thickness?, height?, margin? }).
• link({ href }, child). Wraps a child and registers a PDF Link annotation over its rendered bounding box.
• table({ columns, rows, ... }). Fixed / auto / fractional columns with header/footer rows, dividers, styled cells, and row-level page fragmentation under renderFlow. Cells can be plain nodes or { content, colSpan?, padding?, background?, border?, borderSides?, borderRadius?, align?, valign? }.

Rendering

• flowToPdf(build, options?). The shortest path to bytes. Creates a PDFDocument, hands it to your build(pdf) callback (embed fonts/images there and return the top-level nodes), paginates with renderFlow, and returns the saved Uint8Array. Same options as renderFlow.
• renderFlow(pdf, nodes[], options). Paginates a sequence of top-level children. Top-level vstack nodes may fragment between children; table() fragments between rows and repeats headers on continuation pages. Use keepTogether() or breakInside: "avoid" for atomic blocks. Options: size, margin, header?, footer?, reserveBottom?, title?, author?, subject?, keywords?, creator?, producer?, debug?, warnings?, profile?. Headers and footers receive { pageNumber, totalPages }. Defaults to LETTER (612×792). Pass { size: PageSizes.A4 } for A4. When a top-level child's measured width exceeds the page content area, boxpdf emits a console.warn. Suppress with warnings: false.
• streamFlow(pdf, writable, asyncIterable, options). Incremental page-by-page rendering. Memory stays bounded regardless of page count. Writes PDF bytes to a WritableStream<Uint8Array> as each page closes. See the Streaming section below for the contract.
• renderToPdf(node, options). One-page convenience.
• pageInner(size, margin) / pageContent(size, margin). Compute the inner content width or rectangle of a page.
• render(node, page, x, yTop, parentWidth). Draws a subtree at a known position on an existing PDFPage.
• measure(node, parentWidth). Intrinsic size without drawing.

Pass { debug: true } to outline content boxes in red and margin boxes in orange.

Helpers

• standardFonts(pdf, family?). Embed a built-in pdf-lib family ("helvetica" default, "times", "courier") and get { font, bold, italic, boldItalic } back — ready to drop into any theme. No bytes embedded.
• loadFont(pdf, source, options?). Embed a TTF from URL, bytes, base64, or data URL.
• loadImage(pdf, source). Embed a PNG or JPEG (auto-detected).
• aspectRatio(ratio, { width }) / aspectRatio(ratio, { height }). Derive the missing dimension for fixed-ratio boxes or images.
• formatCurrency(n, { currency, locale }). Intl.NumberFormat wrapper.
• defineStyles({ ... }). Typed identity for reusable style bundles.
• hex("#1f8a4d") / rgb255(31, 138, 77). Color builders.

Loading fonts

Three options.

Bundled bytes via the CLI. Recommended for production.

npx boxpdf font add ./Acme-Regular.ttf=regular ./Acme-Bold.ttf=bold \
  --out src/fonts/acme.ts

Generates src/fonts/acme.ts with export const base64 strings. Then:

import { loadFont } from "boxpdf";
import { regular, bold } from "./fonts/acme.js";

const font = await loadFont(pdf, regular);
const acmeBold = await loadFont(pdf, bold);

Bytes ship inside your bundle. No network round-trip.

The built-in Inter weights.

import { loadFont } from "boxpdf";
import { inter, interBold } from "boxpdf/inter";

const font = await loadFont(pdf, inter);
const bold = await loadFont(pdf, interBold);

boxpdf/inter re-exports the same Inter subset as raw base64 strings (inter, interBold, interItalic) and as embedInter(pdf, { italic?, tabularFigures? }).

Importing boxpdf/inter loads ~325 KB of font bytes plus @pdf-lib/fontkit. The subpath isn't loaded otherwise.

import { embedInter } from "boxpdf/inter";

const { font, bold } = await embedInter(pdf);
const theme = cleanTheme(font, bold);

Pass { tabularFigures: true } to also get tabular-numeral variants for money columns:

const { font, bold, tabularFont, tabularBold } = await embedInter(pdf, {
  tabularFigures: true
});

text(formatCurrency(amount), { size: 12, font: tabularBold, align: "right" });

Fetch from a URL.

const brand = await loadFont(pdf, "https://example.com/Acme-Regular.ttf");

The full TTF gets fetched and subsetted at embed time. On Cloudflare Workers with a warm cache this is fast (~5-15 ms). On a cold cache or in Node you pay the full fetch each time.

loadFont accepts the same { subset?: boolean; features?: { tnum: true } } options regardless of the source. Use features: { tnum: true } to enable tabular numerals.

Streaming output

For long-running document generation, use streamFlow instead of renderFlow. It emits PDF bytes to a WritableStream<Uint8Array> as each page closes. Peak heap is bounded at O(shared resources + one page in flight) regardless of total page count.

import { PDFDocument, StandardFonts } from "pdf-lib";
import { streamFlow, text, cleanTheme } from "boxpdf";

const pdf = await PDFDocument.create();
const font = await pdf.embedFont(StandardFonts.Helvetica);
const bold = await pdf.embedFont(StandardFonts.HelveticaBold);

const { readable, writable } = new TransformStream<Uint8Array, Uint8Array>();
streamFlow(pdf, writable, generate(font, bold)).catch(console.error);

return new Response(readable, {
  headers: { "content-type": "application/pdf" }
});

async function* generate(font, bold) {
  for await (const order of fetchOrders()) {
    yield buildOrderRow(font, bold, order);
  }
}

For Node, adapt a stream.Writable:

import { createWriteStream } from "node:fs";
import { streamFlow, nodeAdapter } from "boxpdf";

const out = nodeAdapter(createWriteStream("./report.pdf"));
await streamFlow(pdf, out, nodes);

Contract

1. All embedFont / embedJpg / embedPng calls must complete before streamFlow. Embedding mid-stream throws.
2. The iterable is consumed one node at a time. Pass a generator.
3. streamFlow closes the writable on success and aborts it on failure. Don't write to it concurrently.
4. ctx.totalPages is not available in headers and footers. Accessing it throws. Use renderFlow if you need "Page X of Y".
5. Output is 0-5% larger than renderFlow's default save().

Memory bench

Peak heap during render. Each measurement runs in its own subprocess. 50 lines of text per page. @react-pdf/renderer included for shape comparison.

streamFlow holds peak heap roughly flat (12 → 25 MB across a 100× workload increase). renderFlow scales roughly linearly with page count. @react-pdf/renderer adds ~2.3 MB per page in this workload and peaks at 2.3 GB by 1000 pages. See docs/design/streaming.md for the design and the chart.

Cloudflare Workers

Both the core and the boxpdf/inter subpath run on Workers without nodejs_compat.

import { Hono } from "hono";
import { cleanTheme, flowToPdf, standardFonts, text } from "boxpdf";

const app = new Hono();

app.get("/receipt.pdf", async (c) => {
  const bytes = await flowToPdf(async (pdf) => {
    const t = cleanTheme(await standardFonts(pdf));
    return [
      text("Thanks!", t.type.h1),
      text("This PDF was generated at the edge.", t.type.body)
    ];
  });
  return new Response(bytes, { headers: { "content-type": "application/pdf" } });
});

export default app;

Examples

Runnable scripts in examples/:

• receipt.ts. Single-page receipt with totals.
• itinerary.ts. Two-band travel itinerary.
• invoice.ts. Multi-page invoice with running header and footer plus keepTogether.
• debug.ts. Layout with { debug: true }.
• themes-showcase.ts. The same receipt rendered in all four themes.
• inter-showcase.ts. Clean theme rendered with Inter.
• flex-shrink.ts. Three URL-overflow behaviors side by side.
• hanging-indent.ts. Paragraph paddingLeft plus negative textIndent for list markers.
• overflow-clipping.ts. Clipped cards with absolute overlays and background images.

Flex-shrink

Opt-in via shrink: number on any child of an hstack or vstack. When the sum of children's intrinsic main-axis sizes exceeds the parent's available space, items with shrink > 0 give up shares proportional to shrink × baseSize. Items with shrink = 0 (the default) are frozen.

hstack(
  { width: 360, gap: 16 },
  text("Customer:", { size: 11, font: bold }),
  text("Mr. Algernon Hephaestus Constantine Pemberton-Smythe III", {
    size: 11, font, shrink: 1
  })
)

Behavior:

• A text child won't shrink below the width of its widest whitespace-separated word. Wrapping breaks on whitespace, not mid-word.
• A single-token string (URL, hash, slug) won't shrink at all and overflows its slot visibly. Two opt-ins lower the floor:
  • maxLines: N. The engine ellipsizes overflow. The text shrinks to its slot and trims with ….
  • breakWords: true. CSS overflow-wrap: break-word. Hard-breaks at character boundaries.
• When shrunk text rewraps to more lines, the container's intrinsic height grows accordingly.
• When one item hits its min-word floor, its remaining shrink weight redistributes to siblings.
• Works on vstack too when the parent has a fixed height smaller than the sum of children.
• link forwards its child's shrink weight, so linked text shrinks and re-wraps like bare text.

See examples/flex-shrink.ts.

Absolute positioning

Boxes can use a small CSS-like positioning model:

vstack(
  { width: 240, height: 120, position: "relative", padding: 16 },
  text("Receipt", { size: 18, font: bold }),
  hstack(
    { position: "absolute", top: 12, right: 12, width: 70 },
    text("PAID", { size: 14, font: bold, align: "center", width: 70 })
  )
)

Behavior:

• Any positioned box establishes the containing block for absolute descendant boxes.
• position: "absolute" removes a vstack or hstack from normal stack flow.
• Absolute boxes render after normal children, so they can be used for stamps, badges, overlays, and watermarks.
• top, right, bottom, and left are point offsets from the nearest positioned ancestor. If there is no positioned ancestor, they resolve against the current render() root.
• If both left and right are set and width is omitted, the box stretches to the remaining width. top plus bottom does the same for height.
• Absolute siblings render by zIndex from low to high. Boxes with the same zIndex keep document order.
• Absolute boxes do not affect parent measurement, gaps, flex grow/shrink, or pagination. Give the containing box a fixed width and height when you need stable placement.

Limitations

• Positioning supports relative containing boxes, out-of-flow absolute boxes, point offsets, zIndex, and stretch from paired edges.
• Font shaping is whatever pdf-lib and fontkit support. Complex Indic, Arabic, and Thai shaping isn't here. Full HarfBuzz requires a different stack, none of which run on Cloudflare Workers today.
• PDF linearization (reordering the byte stream so byte 1 is page 1) is not done. Streaming generation is supported via streamFlow. Linearization is a separate post-process and out of scope.

License

MIT © Erik Aronesty