pdf_edit 0.4.0

A package to edit and fill the fields of PDF forms.

pdf_edit

pdf_edit turns static PDF templates into personalised documents.

Building blocks

• PdfDocumentBuilder – describe template pages and fields. Call build() to produce a PdfDocument ready for rendering.
• PdfDocument – holds the compiled template definition, resolves template bytes and backgrounds automatically, exposes PdfDocumentData, and renders bytes via generate().
• PdfDocumentData – mutable store for field values. Set text, checkbox, and signature bindings on the document after building.
• PdfSignatureData – immutable helper for passing captured ink when you need manual control.
• SignatureRenderer / PaintingSignatureRenderer – strategy for turning captured strokes into PNGs; override it to plug in a custom renderer.
• SignaturePad / SignaturePadController – drop-in Flutter widget for capturing ink strokes and canvas dimensions for signature fields.

Workflow

Follow this flow when generating personalised PDFs:

1. Describe template bindings

import 'dart:ui';

import 'package:pdf_edit/pdf_edit.dart';

final builder = PdfDocumentBuilder(assetPath: 'assets/forms/example.pdf')
  ..text(
    page: 0,
    binding: 'firstName',
    x: 120.0,
    y: 200.0,
    size: const Size(140.0, 20.0),
  )
  ..text(
    page: 0,
    binding: 'lastName',
    x: 120.0,
    y: 230.0,
    size: const Size(140.0, 20.0),
  )
  ..checkbox(
    page: 0,
    binding: 'subscribe',
    x: 360.0,
    y: 230.0,
    size: const Size(16.0, 16.0),
  )
  ..signature(
    page: 0,
    binding: 'signature',
    x: 100.0,
    y: 400.0,
    size: const Size(240.0, 60.0),
  );

final document = builder.build();

2. Populate data bindings

Use a controller per signature field so each binding captures the correct strokes.

final signatureController = SignaturePadController();

document.data
  ..setText(binding: 'firstName', value: 'Ada')
  ..setText(binding: 'lastName', value: 'Lovelace')
  ..setCheckbox(binding: 'subscribe', value: true)
  ..setSignature(binding: 'signature', controller: signatureController);

3. Render the PDF

Call document.generate() to render the document and obtain the raw bytes. If you need different data without mutating the original document, pass an alternate PdfDocumentData via the using parameter.

final Uint8List pdfBytes = await document.generate();
// Persist or share `pdfBytes` as needed.

4. Rehydrate existing PDFs

Existing byte arrays can be wrapped in a PdfDocument for downstream export workflows.

final Uint8List cachedBytes = await storage.loadPdf();
final cachedDocument = PdfDocument.fromBytes(bytes: cachedBytes);
final Uint8List regeneratedBytes = await cachedDocument.generate();

Example app

The /example directory contains a minimal Flutter application that captures a few text fields, an optional checkbox, and a signature before saving the filled PDF to disk using the builder. Use it as a reference implementation or drop-in starter.

Extracting field coordinates with getfields.py

When working with unfamiliar PDFs, you can introspect the form field positions with example/assets/getfields.py:

1. Install PyPDF2 if you have not already:

pip install PyPDF2

2. Run the script, pointing it at your template:

python example/assets/getfields.py path/to/form.pdf

It prints a summary of each field and writes a JSON file next to the PDF (you can override the destination with --output). The flutterConfig values in the JSON map directly to the coordinates expected by PdfDocumentBuilder.

Contributions and issues are welcome. If you need support for additional field types or have ideas to streamline authoring, please open a ticket.

Licensed under the BSD 3-Clause License. See LICENSE for details.