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 A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections.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

use chilkat();

$success = 0;

#  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 = chilkat::CkPdf->new();
$success = $pdf->LoadFile("qa_data/pdf/grand_canyon_hiking_guide.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

#  How much of this file is superseded revisions?
$json = chilkat::CkJsonObject->new();
$jsonOut = chilkat::CkJsonObject->new();
$success = $pdf->Optimize("audit",$json,$jsonOut);
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

print "fileSize:     " . $jsonOut->IntOf("fileSize") . "\r\n";
print "oldRevisions: " . $jsonOut->IntOf("usage.oldRevisions.bytes") . "\r\n";

#  Drop them, and nothing else, so that the saving is attributable.
$json->UpdateBool("compressUncompressed",0);
$json->UpdateBool("recompressFlate",0);
$json->UpdateBool("replaceLegacyFilters",0);
$json->UpdateBool("imagePredictors",0);
$json->UpdateBool("dedupeStreams",0);
$json->UpdateBool("dedupeObjects",0);
$json->UpdateBool("removeUnreferenced",0);
$json->UpdateBool("removeUnusedResources",0);
$json->UpdateBool("removeUnusedLayers",0);
$json->UpdateBool("coalesceContent",0);
$json->UpdateBool("tidyContent",0);
$json->UpdateBool("subsetFonts",0);
$json->UpdateBool("dropOldRevisions",1);

$success = $pdf->Optimize("optimize",$json,$jsonOut);
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

$success = $pdf->WriteFile("qa_output/grand_canyon_one_revision.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\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 = chilkat::CkFileAccess->new();
print "bytesSaved (reported): " . $jsonOut->IntOf("bytesSaved") . "\r\n";
print "written file:          " . $fac->FileSize("qa_output/grand_canyon_one_revision.pdf") . "\r\n";