VellumPdf.Signing 1.9.0

VellumPdf

A modern, dependency-free PDF generation library for .NET 10, implemented clean-room from the open ISO 32000 standard.

Status: stable. The public API is locked (analyzer-enforced) and the library targets .NET 10. Core features are CI-validated — including PDF/A-2a/2b/2u and PDF/UA-1 conformance proven on every push with veraPDF.

Why VellumPdf

• Zero runtime dependencies. The core is built entirely on the .NET base class library — no native binaries, no third-party packages. (The optional signing package is the sole exception: it uses System.Security.Cryptography.Pkcs.)
• AOT- and trim-ready. Ships as managed DLLs; ideal for Native AOT, trimming, containers, and serverless. A Native-AOT smoke test guards this.
• Unicode-first text. Embeds and subsets TrueType and OpenType-CFF fonts, emits composite (CID) fonts with subset tags, and writes ToUnicode maps so output stays searchable and copy-paste-able.
• Two API tiers. A low-level canvas for precise drawing, and a high-level document/layout engine with paragraphs, headings, lists, tables, images, and automatic pagination.
• Built for the hard standards. PDF/A-2a (accessible archival) and PDF/UA-1 (universal accessibility) are implemented and CI-validated with veraPDF, alongside PDF/A-2b/2u, PAdES digital signatures, and interactive AcroForms.
• Permissive license. Apache-2.0 — free to use in proprietary products.

Packages

Package	NuGet	Status	Description
VellumPdf.Kernel		Stable	Object model, canvas, Standard-14 fonts, TrueType/OpenType embedding + subsetting, images (JPEG/PNG/BMP/GIF/TIFF/JBIG2/JPEG 2000), AES-256 encryption, object/cross-reference streams, AcroForm fields, tagged-PDF structure tree, PDF/A-2 metadata, DeviceCMYK and ICC-based colour with configurable output intents, and opt-in linearization (Linearize) for fast-web-view first-page rendering.
VellumPdf.Fonts.Standard14		Stable	Optional, embeddable metric-compatible substitutes for the standard-14 fonts (Liberation Sans/Serif/Mono, SIL OFL 1.1, covering the Helvetica/Times/Courier families). The built-in Standard14 fonts are not embedded — fine for ordinary PDFs but disallowed by PDF/A's font-embedding rule; doc.EmbedStandard14Font(...) registers a subset, embedded substitute so standard-14-style text is PDF/A-conformant without a caller-supplied font program. (Symbol and ZapfDingbats are not covered.)
VellumPdf.Layout		Stable	High-level document builder: paragraphs, headings, lists, tables, images, pie charts, header/footer bands, bookmarks, and automatic pagination.
VellumPdf.Signing		Stable	PAdES / PKCS#7 detached digital signatures with RFC-3161 signature timestamps and long-term validation. Levels B-T, B-LT (embedded OCSP/CRL in a /DSS), and B-LTA (archive document timestamp), via pluggable timestamp and revocation clients.
VellumPdf.Reader		Preview	Opens existing PDFs (classic cross-reference tables, cross-reference and object streams, hybrid-reference files; unencrypted) and exposes the catalog, signatures, and decoded stream data. The basis for the signing LTV path, the conformance validator, and a general reader.
VellumPdf.Conformance		Preview	In-process PDF/A-2b/2u/2a and PDF/UA-1 preflight: runs clean-room conformance rules authored from the ISO specifications and returns machine-readable assertions (rule id, ISO clause, severity, object reference) — no external veraPDF Docker image needed. AOT- and trim-ready (rules registered explicitly, no reflection). Covers file structure, colour and output intents (including ICC profile validity and ICCBased-CMYK overprint), transparency, images and XObjects (including a JPEG2000 codestream parser), fonts (an in-process sfnt font-program parser for glyph presence and widths, embedded-CMap CID/WMode/usecmap checks), content streams (ISO 32000-1 operator, inline-image-filter, and graphics-state validation), digital signatures (a zero-dependency CMS/ASN.1 reader for §6.4.3), annotations, interactive forms, actions, and XMP metadata (via an in-process XMP parser), plus the 2u/2a deltas and a tagged-structure walker for the PDF/UA-1 (ISO 14289-1) accessibility checks. Build-verified veraPDF parity is about 99% for PDF/A-2b/2u/2a and PDF/UA-1; the only gaps are five checks tracked in follow-up issues — three with a predefined-CJK-CMap sub-condition that needs a conformant CJK font asset to cross-validate, and two that need a subsystem outside this release (a PDF/A-1 profile, reader decryption). Every rule's positive and negative paths are cross-validated against veraPDF in CI.
VellumPdf.Cli		Stable	The vellum-preflight command-line validator: checks a PDF against PDF/A-2b/2u/2a and PDF/UA-1 with the in-process VellumPdf.Conformance engine — no JVM or Docker. Ships as a cross-platform .NET tool (dotnet tool install -g VellumPdf.Cli) and self-contained Native-AOT binaries. Text, JSON, and SARIF 2.1.0 output; file, glob, directory, and stdin inputs; exit codes 0 (conformant), 1 (non-conformant), 2 (usage or I/O error).
VellumPdf.Barcodes		Preview	Six symbologies: QR (including Micro QR M1-M4), PDF417, Code 128 (plain and GS1-128), EAN-13/EAN-8/UPC-A with EAN-2/EAN-5 add-ons, and ITF-14, rendered as vector rectangles through a low-level PdfCanvas extension or the Document.Add flow API. Round-trip decoding is verified in CI against zxing-cpp.

Install

# Core
dotnet add package VellumPdf.Layout
dotnet add package VellumPdf.Kernel

# Add-ons
dotnet add package VellumPdf.Signing
dotnet add package VellumPdf.Fonts.Standard14
dotnet add package VellumPdf.Barcodes

# Preview
dotnet add package VellumPdf.Reader
dotnet add package VellumPdf.Conformance

# Tooling (.NET global tool)
dotnet tool install -g VellumPdf.Cli

VellumPdf.Layout pulls in VellumPdf.Kernel as a dependency, so most apps only need the first line. Quick start below shows VellumPdf.Layout/VellumPdf.Kernel in use, and Barcodes shows VellumPdf.Barcodes.

Quick start

dotnet add package VellumPdf.Layout

using VellumPdf.Document;          // PdfConformance
using VellumPdf.Fonts;             // Standard14
using VellumPdf.Layout;            // Document
using VellumPdf.Layout.Core;       // TextStyle
using VellumPdf.Layout.Elements;   // Paragraph, Heading
using VellumPdf.Layout.Elements.Table; // TableElement

// Basic document — defaults to A4.
using var doc = new Document();
doc.SetDefaultFont(new TextStyle { Font = Standard14.Helvetica, FontSize = 11 });
doc.Add(new Heading("Hello, world!"));
doc.Add(new Paragraph("Generated with VellumPdf — no native dependencies."));
doc.Save("hello.pdf");

// PDF/A-2b archival document. PDF/A requires every glyph to come from an
// embedded font, so load a TrueType font and use it for all text.
using var archive = new Document { Conformance = PdfConformance.PdfA2b };
var font = archive.LoadTrueTypeFont("/path/to/DejaVuSans.ttf");
var style = new TextStyle { FontRef = font, FontSize = 12 };

archive.Add(new Paragraph("This document validates as PDF/A-2b.", style));

var table = new TableElement { DefaultCellStyle = style };
table.SetColumnWidths(200, 200);
table.AddHeaderRow().AddCell("Item").AddCell("Value");
table.AddRow().AddCell("Format").AddCell("PDF/A-2b");
archive.Add(table);

archive.Save("archive.pdf");

Low-level Kernel API

For precise canvas control, bypass the Layout engine and write directly to the PDF content stream:

using VellumPdf.Canvas;    // PdfCanvas
using VellumPdf.Document;  // PdfDocument, PageSize
using VellumPdf.Fonts;     // Standard14

using var doc = new PdfDocument();
var page = doc.AddPage(PageSize.A4);
var font = doc.UseFont(Standard14.Helvetica);
var canvas = new PdfCanvas(page);

canvas
    .BeginText()
    .SetFont(font, 12)
    .SetTextMatrix(1, 0, 0, 1, 72, 720)
    .ShowText("Hello from the Kernel API!")
    .EndText();

canvas.Finish();

using var stream = File.OpenWrite("kernel-hello.pdf");
doc.Save(stream);

For a full walkthrough of the canvas, graphics primitives, and font handling, see docs/kernel-guide.md.

Barcodes

dotnet add package VellumPdf.Barcodes

using VellumPdf.Barcodes;

// Flow API: adds a QR Code to the document like any other element.
doc.Add(new QrCode("https://example.com") { TargetWidth = 120 });

// Low-level API: draws directly onto a PdfCanvas, with human-readable text below the bars.
canvas.DrawBarcode(new EanBarcode(EanSymbology.Ean13, "400638133393"), 72, 700, font);

QR (including Micro QR), PDF417, Code 128, EAN-13/EAN-8/UPC-A, and ITF-14 are all covered; see docs/barcodes-guide.md for sizing, human-readable text, GS1/FNC1, and the QR charset policy. QR Code is a registered trademark of DENSO WAVE INCORPORATED.

Conventions

• Units. All coordinates and sizes are in PDF user-space points (1 pt = 1/72 inch). PageSize provides the common ISO-A sizes plus a PageSize.Mm(width, height) helper for custom millimetre dimensions.
• Synchronous I/O. Saving, signing, and the font/image loaders are synchronous by design for 1.0 — there is no async surface. Offload to Task.Run if you need to keep a thread free.

Validation & CI

Correctness is enforced on every push by running real external validators as CI oracles — a missing tool fails the build, so the gates can never silently skip:

• qpdf --check — structural integrity of every generated document type.
• pdftotext (poppler) — text-extraction round-trip proving ToUnicode maps.
• pdfsig (poppler) — signature validity for PAdES documents.
• veraPDF (official verapdf/cli Docker image) — strict PDF/A-2a/2b/2u and PDF/UA-1 conformance over embedded-font, table, image, and tagged documents. A non-compliant report fails CI with the full rule list attached.
• zxing-cpp — decode round-trip for every barcode symbology: each generated PDF is rasterized with pdftoppm and decoded back, so the CI oracle catches encoding regressions a unit test's own vectors could miss.

Command-line preflight

vellum-preflight validates a PDF against PDF/A-2b/2u/2a and PDF/UA-1 in-process — no JVM or Docker. Install it as a cross-platform .NET tool, or download a self-contained native binary (Windows x64/Arm64, macOS Arm64, Linux x64) from the latest release.

dotnet tool install -g VellumPdf.Cli   # then run: vellum-preflight <file>

# Does the PDF honour the conformance level it claims? (pass/fail, with reasons)
vellum-preflight invoice.pdf

# A specific profile, machine-readable output
vellum-preflight invoice.pdf -p 2u -f json -o report.json

# Validate a whole tree; fail CI on any error
vellum-preflight ./out --recurse --fail-on error -q

# Several profiles at once
vellum-preflight report.pdf -p 2b,2a,ua1

# See exactly what the tool checks for a profile
vellum-preflight --coverage 2b

Every report states three things: what failed (rule id, ISO clause, reason, offending object), what passed, and what was not fully evaluated — so a clean result is never mistaken for an absolute guarantee. Exit codes are 0 (conformant), 1 (non-conformant), and 2 (usage or I/O error).

Roadmap

Planned direction, tracked as GitHub milestones. These are scopes, not commitments — the milestones carry no due dates, and nothing past 1.9.0 has shipped yet.

VellumPdf.Reader, VellumPdf.Conformance, and VellumPdf.Barcodes are marked Preview in the table above; expect their public surfaces to settle as these milestones land.

Building

Requires the .NET 10 SDK.

dotnet build VellumPdf.slnx
dotnet test  VellumPdf.slnx

The veraPDF conformance gate runs automatically in CI; to reproduce it locally, install veraPDF (or use its Docker image) so the verapdf CLI is on your PATH, then run the oracle tests.

License & provenance

Licensed under the Apache License 2.0. VellumPdf is an original, independent implementation written solely from open published specifications; see NOTICE and docs/architecture.md.