.NET PDF Library - Compress PDFs

using Syncfusion.Pdf.Parsing;
using Syncfusion.Pdf;

// Open a file stream to read the input PDF file.
using (FileStream fileStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read))
{ 
    // Create a new PdfLoadedDocument object from the file stream.
    using (PdfLoadedDocument loadedDocument = new PdfLoadedDocument(fileStream))
    { 
        // Create a new PdfCompressionOptions object.
        PdfCompressionOptions options = new PdfCompressionOptions(); 
        // Enable image compression and set image quality.
        options.CompressImages = true; 
        options.ImageQuality = 50; 
        // Enable font optimization.
        options.OptimizeFont = true; 
        // Enable page content optimization.
        options.OptimizePageContents = true; 
        // Remove metadata from the PDF.
        options.RemoveMetadata = true; 
        // Compress the PDF document.
        loadedDocument.Compress(options);
        // Save the document into a memory stream.
        using (MemoryStream outputStream = new MemoryStream()) 
        { 
            loadedDocument.Save(outputStream); 
        } 
    } 
}