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 A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections.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

var success = false;

//  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

var pdf = new CkPdf();
success = pdf.LoadFile("qa_data/pdf/grand_canyon_hiking_guide.pdf");
if (success == false) {
    console.log(pdf.LastErrorText);
    return;
}

//  How much of this file is superseded revisions?
var json = new CkJsonObject();
var jsonOut = new CkJsonObject();
success = pdf.Optimize("audit",json,jsonOut);
if (success == false) {
    console.log(pdf.LastErrorText);
    return;
}

console.log("fileSize:     " + jsonOut.IntOf("fileSize"));
console.log("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);

success = pdf.Optimize("optimize",json,jsonOut);
if (success == false) {
    console.log(pdf.LastErrorText);
    return;
}

success = pdf.WriteFile("qa_output/grand_canyon_one_revision.pdf");
if (success == false) {
    console.log(pdf.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.
var fac = new CkFileAccess();
console.log("bytesSaved (reported): " + jsonOut.IntOf("bytesSaved"));
console.log("written file:          " + fac.FileSize("qa_output/grand_canyon_one_revision.pdf"));