Dart Requires Chilkat v11.7.0+

Remove a PDF's Old Revisions

See more PDF Optimization Examples

Demonstrates dropOldRevisions. A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections. The audit reports them as "oldRevisions", and dropping them is often the single largest saving in a real document. Dropping them requires a full rewrite, which is why it invalidates existing digital signatures. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // The PDF used in this example is available at grand_canyon_hiking_guide.pdf

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/grand_canyon_hiking_guide.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // How much of this file is superseded revisions?
  final json = CkJsonObject();
  final jsonOut = CkJsonObject();
  try {
    pdf.optimize('audit', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('fileSize:     ${jsonOut.intOf('fileSize')}');
  print('oldRevisions: ${jsonOut.intOf('usage.oldRevisions.bytes')}');

  // Drop them, and nothing else, so that the saving is attributable.
  json.updateBool('compressUncompressed', false);
  json.updateBool('recompressFlate', false);
  json.updateBool('replaceLegacyFilters', false);
  json.updateBool('imagePredictors', false);
  json.updateBool('dedupeStreams', false);
  json.updateBool('dedupeObjects', false);
  json.updateBool('removeUnreferenced', false);
  json.updateBool('removeUnusedResources', false);
  json.updateBool('removeUnusedLayers', false);
  json.updateBool('coalesceContent', false);
  json.updateBool('tidyContent', false);
  json.updateBool('subsetFonts', false);
  json.updateBool('dropOldRevisions', true);

  try {
    pdf.optimize('optimize', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    pdf.writeFile('qa_output/grand_canyon_one_revision.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The saving is an estimate: what the old revisions occupied is known exactly, but the writer
  // decides the final layout.  Measure the written file for the real number.
  final fac = CkFileAccess();
  print('bytesSaved (reported): ${jsonOut.intOf('bytesSaved')}');
  print('written file:          ${fac.fileSize('qa_output/grand_canyon_one_revision.pdf')}');
}