How to remove unused objects from PDF file (Tutorial)

PDF files sometimes contain objects which are never used. This increases the file size and is wasteful. This tutorial shows you how to reduce the file size by removing unused objects from PDF in Java or using the command line.
 
The PDF file format is not natively supported by Java, so to remove unused objects from a PDF file you will need to download an external library. This tutorial uses JPedal.
 

How to remove unwanted objects from a PDF file programmatically

1. Add JPedal to your class or module path (download the trial jar)
2. Create a File handle pointing to the PDF file
3. Run the below code:
   

   PdfOptimizer.optimizePDF(
           new File("/path/to/input.pdf"),
           new File("/path/to/output.pdf"),
           PdfOptimizer.Optimization.REMOVEUNUSEDOBJECTS
   );
   

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   Download Jar

Using the command line

1. Download the JPedal trial jar
2. Run the following command:
   

   java -cp jpedal.jar org.jpedal.tools.PdfOptimizer --removeUnusedObjects inputFile outputFile

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You can expand your understanding of the PDF format by reading our other articles. Similarly, if there is a specific term for PDF you would like to know more about, our PDF Glossary has an extensive list of common terms.

Viewer viewer = new Viewer();
viewer.setupViewer();
viewer.executeCommand(ViewerCommands.OPENFILE, "pdfFile.pdf");

//Convenience static method (see class for additional options)
ExtractClippedImages.writeAllClippedImagesToDir("inputFileOrDirectory", "outputDir", "outputImageFormat", new String[] {"imageHeightAsFloat", "subDirectoryForHeight"});

//Convenience static method (see class for additional options)
ExtractTextAsWordList.writeAllWordlistsToDir("inputFileOrDirectory", "outputDir", -1);

//Convenience static method (see class for additional options)
ArrayList resultsForPages = FindTextInRectangle.findTextOnAllPages("/path/to/file.pdf", "textToFind");

PrintPdfPages print = new PrintPdfPages("C:/pdfs/mypdf.pdf");

if (print.openPDFFile()) {
    print.printAllPages("Printer Name");
}

//Convenience static method (see class for additional options)
ExtractClippedImages.writeAllClippedImagesToDir("inputFileOrDirectory", "outputDir", "outputImageFormat", new String[] {"imageHeightAsFloat", "subDirectoryForHeight"});