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 A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections.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

Dim success As Boolean = 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

Dim pdf As New Chilkat.Pdf
success = pdf.LoadFile("qa_data/pdf/grand_canyon_hiking_guide.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  How much of this file is superseded revisions?
Dim json As New Chilkat.JsonObject
Dim jsonOut As New Chilkat.JsonObject
success = pdf.Optimize("audit",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("fileSize:     " & jsonOut.IntOf("fileSize"))
Debug.WriteLine("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) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


success = pdf.WriteFile("qa_output/grand_canyon_one_revision.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  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.
Dim fac As New Chilkat.FileAccess
Debug.WriteLine("bytesSaved (reported): " & jsonOut.IntOf("bytesSaved"))
Debug.WriteLine("written file:          " & fac.FileSize("qa_output/grand_canyon_one_revision.pdf"))