dart-pdf: Flutter PDF editor and renderer

[!TIP] Want the app, not the SDK? DartPDF is the official PDF editor built on this library. Edit, annotate, sign, and fill PDFs entirely on your device, with no account and no uploads. Get it at dart-pdf.com or open it in your browser.

Need to complete a form? Fill and sign a PDF with DartPDF explains existing fields, flat forms, drawn signatures, and saving a checked copy.

An open-source Flutter PDF editor, viewer, and renderer written entirely in Dart. No PDFium, no platform channels.

The goal is a PSPDFKit-class SDK built natively for Flutter: a fast viewer, a full annotation suite with appearance-stream generation, AcroForm filling, page manipulation, and editing that preserves digital signatures.

Feature parity is only the foundation. The UX vision defines the product north star, the journeys that matter, how their quality is measured, and the definition of done for user-facing work.

Status: the roadmap below is complete. COS parsing with xref recovery, signature-preserving incremental updates with encrypt-on-write, a content-stream interpreter with TrueType/CFF/Type3 font rendering, mesh shadings, ICC color, pure-Dart CCITT/JBIG2/JPEG 2000 decoders, a zoomable Flutter viewer with text selection and search, inferred text reflow, annotation authoring and flattening, AcroForm filling, page manipulation, digital signatures with trust-store chain validation, content editing, and the full editing UI: tools, panels, forms, touch/stylus input, theming, and a sync surface for collaborative annotation stores.

Live demo: https://dart-pdf-demo.web.app (the example app built for the web; it opens onto a six-page feature showcase, and the open button loads your own PDF).

Developer overview: Flutter PDF editor

Step-by-step integration: How to add PDF editing to a Flutter app with installation, architecture, supported editing features, and benchmarks.

Visual render results, browsable directly in GitHub: the checked-in PDF.js corpus comparison gallery shows PDF.js baselines, Dart renders, and diffs side by side, and the Ghent Output Suite render gallery shows every print-conformance page we rasterize (our own renders, which are the baselines - so no diff column).

Merge PDFs

import 'package:pdf_document/pdf_document.dart';

final mergedBytes = PdfMerger.merge([firstPdfBytes, secondPdfBytes]);

The bytes-only API runs on desktop, mobile, and web. It preserves the first PDF's encryption and viewing settings, imports form fields and bookmarks, and remaps named links. See merge options and collision rules.

In DartPDF, choose Insert document… from the app menu to insert a PDF after the current page. Dropping PDFs on the thumbnail strip inserts at the marked position; dropping on the document offers Insert pages to append them. Each inserted file is one undo step and uses the existing save/recovery session.

Reduce file size

In DartPDF, choose Reduce file size… from the app menu. Start with Lossless, or choose Screen, eBook, or Print to trade image resolution for a smaller file. Advanced settings control individual passes, target DPI, and JPEG quality. Review the before/after sizes and category breakdown, then Save copy using the platform's save/download/share flow.

The library exposes the same optimiser through PdfCompressor.optimize and PdfEditor.compress. See compression options and supported content.

Performance

The default viewer has not reached PDFium interaction parity yet. The most recent real-document checkpoint (2 October 2026, commit fadf7760) used five interleaved DartPDF/PDFium runs in Chrome 154 on an M1 Pro, a 1400×1000 viewport, and the default JS/CanvasKit web build. The input was a locally supplied 62-page, 24.1 MB illustrated PDF; the journey opened it, jumped to pages 3 and 47, zoomed to 1.72×, and drove matched wheel gestures. Lower ratios are better.

user-visible metric	DartPDF p50 / p95	PDFium p50 / p95	ratio p50 / p95
open to stable visual	711 / 757 ms	1264 / 1411 ms	0.56× / 0.54×
page first visual change	24 / 31 ms	19 / 22 ms	1.26× / 1.39×
page stable visual	271 / 357 ms	118 / 121 ms	2.30× / 2.95×
zoom stable visual	44 / 47 ms	19 / 25 ms	2.32× / 1.92×
wheel journey	413 / 919 ms	972 / 1022 ms	0.42× / 0.90×
wheel rAF interval p95	83 ms	17 ms	4.96×
peak browser RSS p50	2167 MiB	1887 MiB	1.15×

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