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 A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections.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

#include <CkPdf.h>
#include <CkJsonObject.h>
#include <CkFileAccess.h>

void ChilkatSample(void)
    {
    bool 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

    CkPdf pdf;
    success = pdf.LoadFile("qa_data/pdf/grand_canyon_hiking_guide.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    //  How much of this file is superseded revisions?
    CkJsonObject json;
    CkJsonObject jsonOut;
    success = pdf.Optimize("audit",json,jsonOut);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "fileSize:     " << jsonOut.IntOf("fileSize") << "\r\n";
    std::cout << "oldRevisions: " << jsonOut.IntOf("usage.oldRevisions.bytes") << "\r\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);

    success = pdf.Optimize("optimize",json,jsonOut);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    success = pdf.WriteFile("qa_output/grand_canyon_one_revision.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        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.
    CkFileAccess fac;
    std::cout << "bytesSaved (reported): " << jsonOut.IntOf("bytesSaved") << "\r\n";
    std::cout << "written file:          " << fac.FileSize("qa_output/grand_canyon_one_revision.pdf") << "\r\n";
    }