PHP 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 A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections.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. Chilkat2 PHP

<?php

use Chilkat2\FileAccess;
use Chilkat2\JsonObject;
use Chilkat2\Pdf;

// 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

$pdf = new Pdf();
try {
    $pdf->LoadFile('qa_data/pdf/grand_canyon_hiking_guide.pdf');

    // How much of this file is superseded revisions?
    $json = new JsonObject();
    $jsonOut = new JsonObject();
    $pdf->Optimize('audit', $json, $jsonOut);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo 'fileSize:     ', $jsonOut->IntOf('fileSize'), "\n";
echo 'oldRevisions: ', $jsonOut->IntOf('usage.oldRevisions.bytes'), "\n";

// 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);

    $pdf->WriteFile('qa_output/grand_canyon_one_revision.pdf');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// 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.
$fac = new FileAccess();
echo 'bytesSaved (reported): ', $jsonOut->IntOf('bytesSaved'), "\n";
echo 'written file:          ', $fac->FileSize('qa_output/grand_canyon_one_revision.pdf'), "\n";