PDF Engine

Overview of PNPDF, PrintNow's custom PDF generation library built for print production workflows.

PNPDF is PrintNow's custom PDF generation library, purpose-built to replace the third-party PdfSharp 1.35 dependency. It is a write-only library designed for professional print production — generating press-ready PDFs with full CMYK support, spot colors, ICC profiles, and PDF/X-4 compliance. PNPDF has zero external dependencies, targets .NET Standard 2.0, and integrates seamlessly across the PrintNow platform.

Every PDF that PrintNow generates — customer proofs, merged order files, single-page exports, and print-ready output — flows through PNPDF.

Why PNPDF Was Built

PdfSharp 1.35 served as PrintNow's PDF library for years, but it lacked critical features for professional print production:

No native CMYK color space support
No spot color or Pantone support
No PDF/X-4 compliance for press-ready output
No ICC profile embedding
No font subsetting (embedded full fonts, inflating file sizes)
No transparency blend modes beyond basic opacity
Limited to PDF 1.4 output

PNPDF was built as a drop-in API replacement with matching class names and method signatures, while adding the advanced features print production demands.

Capabilities

Color Management

Feature	Description
RGB colors	Standard RGB color space with 0-255 or 0.0-1.0 value ranges.
CMYK colors	Native DeviceCMYK color space for print-accurate color output.
Grayscale	DeviceGray color space for monochrome output.
Spot colors	Named separation colors (e.g., Pantone) with tint support and CMYK/RGB alternates.
ICC profiles	Embed ICC profiles for color-managed workflows. Built-in profiles include FOGRA39, FOGRA51, GRACoL, SWOP, and Japan Color.
Rich black	Utilities for standard rich black formulations and ink coverage limits.

Graphics and Drawing

Feature	Description
Shapes	Rectangles, ellipses, arcs, pies, lines, and complex paths with Bezier curves.
Gradients	Linear and radial gradients with multi-stop support.
Patterns	Tiling patterns with rotation and scale transformations.
Transparency	Independent fill and stroke opacity with 16 blend modes (Multiply, Screen, Overlay, etc.).
Clipping	Clipping paths with even-odd and winding fill modes.
Transformations	Translate, rotate, scale, and custom matrix transforms with save/restore state.
Overprint	Separate fill and stroke overprint control for press-accurate ink behavior.

Text and Fonts

Feature	Description
Font formats	TrueType (.ttf) and CFF/OpenType (.otf) with automatic format detection.
Font subsetting	Embeds only the glyphs used in the document, significantly reducing file size.
Font styles	Regular, Bold, Italic, BoldItalic, Underline, and Strikeout with combinations.
Text alignment	Nine alignment positions (TopLeft, Center, BottomRight, etc.).
Text measurement	Accurate width and height measurement for layout calculations.
Text to path	Convert text to vector outlines for effects and clipping.

Images

Feature	Description
JPEG	RGB and CMYK JPEG with passthrough (no re-encoding). ICC profile preservation.
PNG	RGB, RGBA (alpha extracted as soft mask), Grayscale, and Indexed color. ICC profile preservation.
Deduplication	Images embedded once and referenced by content hash, even when drawn multiple times.
PDF templates	Import existing PDF pages as templates via `XPdfForm` for overlays and backgrounds.

Print Production

Feature	Description
PDF/X-4	Full compliance with validation. Output intent embedding and XMP metadata generation.
Page boxes	MediaBox, TrimBox, BleedBox, ArtBox, and CropBox for print preparation.
Print marks	Crop marks, registration marks, and color bars.
PDF versions	Output as PDF 1.0 through 2.0. Object streams and cross-reference streams for PDF 1.5+.
Compression	FlateDecode compression with optional object streams for compact file sizes.

Dieline Spot Plates

For Print CAD products, the print-ready PDF carries the dieline as separate spot-color plates, one per line type. A converter can then image cuts, creases, seals, windows and zippers separately.

One plate per line type. Each line type prints on a spot plate named by its Spot Name in Dieline Colors. This includes the flexible packaging types Seal, Window, Zipper, Valve and Tear Notch.
Custom styles. A custom line style drawn in Print CAD gets its own plate only after it is mapped in Dieline Colors. Custom styles are drawn as lines only (stroke, no fill). Unmapped custom styles are left out of the PDF.
Exact names. Spot names are kept exactly as typed, including spaces, accents and symbols, so they match the converter's separation names.
Only the chosen variant. Lines in a conditional group that is off for the customer's options (for example, no window) don't appear on any plate.
Same output everywhere. Files from the remote merge service have the same plates as files generated in the store.

How It Fits in the Platform

PNPDF sits at the foundation of PrintNow's PDF pipeline:

PdfManager (Data layer) — the rendering engine that converts product designs into PDF pages. It processes text, images, and drawing spaces, calling PNPDF to compose the final output.
PdfLibraryCompat — an abstraction layer between PdfManager and PNPDF, providing a stable interface during the migration from PdfSharp.
MergeManager — the orchestration layer that coordinates order and product merges, calling PdfManager for each product and assembling the results.

Product Design (JSON)
    ↓
PdfManager (rendering engine)
    ↓
PdfLibraryCompat (abstraction)
    ↓
PNPDF (PDF generation)
    ↓
PDF file → Azure Blob Storage or Local File System

Every product ordered through the storefront, remerged by an admin, or triggered via the Enterprise API flows through this pipeline.

Merge Engine — how PDFs are assembled into final order output
Admin Remerge — trigger and monitor PDF remerges from the admin
Orders — order management where merged PDFs are accessed
Products — product configuration that feeds the PDF pipeline

PDF Engine

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