SYNCFUSION BLOG

7 ways to compress PDF files in C#, VB.NET

Syncfusion Essential PDF is a .NET PDF library that can be used to optimize or compress your PDF documents. Reducing the PDF file size can help you by optimizing bandwidth cost, network transmission, and digital storage. It is especially useful in areas like archiving, emailing, and using PDF documents in web-based applications. Essential PDF supports the following optimizations:

  • Shrinking all images.
  • Optimizing fonts.
  • Removing metadata.
  • Optimizing page content.
  • Disabling incremental updates.
  • Removing or flattening form fields.
  • Removing or flattening annotations.

In this blog we will look at each of these optimizations and how to implement them.

Reducing PDF file size by shrinking all images

PDF files may contain many images. Removing the images from a PDF file is usually not an option since they are necessary for many PDFs. Downsampling the images will decrease the number of pixels and is possibly the most effective way to reduce PDF file size. The user can control the PDF file size with respect to the quality of the image.

//Create a new compression option object.
PdfCompressionOptions options = new PdfCompressionOptions();
options.CompressImages = true;
//Image quality is a percentage.
options.ImageQuality = 10;

Reducing PDF file size by optimizing fonts

Font resources will also result in large file sizes. Embedded fonts in a PDF document may contain unused glyphs and unwanted font tables—all of which can be removed to make a smaller PDF.
PdfCompressionOptions options = new PdfCompressionOptions();
options.OptimizeFont = true;

Reducing PDF file size by removing metadata

Sometimes metadata in a PDF document will not be needed and can be removed from the PDF file to reduce its size.

PdfCompressionOptions options = new PdfCompressionOptions();
options.RemoveMetadata = true;

Reducing PDF file size by optimizing page contents

Optimizing the page contents will remove unwanted commented lines, white spaces, convert end-of-line characters to spaces and compress all uncompressed contents.

PdfCompressionOptions options = new PdfCompressionOptions();
options.OptimizePageContents = true;

Reducing PDF file size by disabling incremental updates

The content of a PDF file can be updated incrementally without rewriting the entire file. Changes are appended to the end of the file, leaving its original contents intact. Disabling the incremental update will rewrite the entire file, which results in a smaller PDF.

//Load the existing PDF document.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(@"input.pdf");
//Restructure the complete document.
loadedDocument.FileStructure.IncrementalUpdate = false;

Reducing PDF file size by removing form fields

Removing or flattening form fields can help reduce your file size. When form fields and their values are not necessary, they can be removed. When they are necessary but require no further editing, they can be flattened. Both of these actions will result in a reduced file size. 

public void RemoveFormFields(PdfLoadedDocument ldoc, bool flatten)
{
    if (flatten)
    {
        ldoc.Form.Flatten = true;
    }
    else
    {
        int count = ldoc.Form.Fields.Count;
        for (int i = count - 1; i >= 0; i--)
        {
            ldoc.Form.Fields.RemoveAt(i);
        }
    }
}

Reducing PDF file size by removing annotations

Removing or flattening annotations can help reduce your file size. Annotations and their contents can be removed when they are not needed. When they are necessary but do not require additional editing, they can be flattened. Both of these options will result in a reduced file size.

public void RemoveAnnotations(PdfLoadedDocument ldoc, bool flatten)
{
    foreach(PdfPageBase page in ldoc.Pages)
    {
        if (flatten)
        {
           page.Annotations.Flatten = true;
        }
        else
        {
            int count = page.Annotations.Count;
            for (int i = count - 1;i >= 0; i--)
            {
              page.Annotations.RemoveAt(i);
            }
        }
    }  
}


PDF compression options

A sample demonstrating the available compression options in Essential PDF can be downloaded here: OptimizePDFSample.zip.

Wrapping up

As you can see, Essential PDF provides a variety of optimizing mechanisms for compressing a PDF document. Use them effectively to generate compressed documents for increased efficiency and productivity in a document management system. Take a moment to peruse the documentation, where you’ll find other options and features, all with accompanying code examples.

If you are new to our PDF library, it is highly recommended that you follow our Getting Started guide.

If you’re already a Syncfusion user, you can download the product setup here. If you’re not yet a Syncfusion user, you can download a free, 30-day trial here.

If you have any questions or require clarifications about these features, please let us know in the comments below. You can also contact us through our support forum or Direct-Trac. We are happy to assist you!


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