Efficient PDF Compression in Python (A Practical Guide)

Large PDF files can slow down email delivery, break upload limits, and consume unnecessary storage. This is especially common in PDFs that include high-resolution scans, images, or embedded fonts. If you're working with Python and need to automate PDF compression without compromising quality, this guide will help you get started.

In this tutorial, you’ll learn how to compress PDF files in Python using the Spire.PDF for Python library. We'll cover several effective techniques, including image recompression, font optimization, metadata removal, and batch compression—perfect for web, backend, or desktop applications.

Table of Contents

• Common Scenarios Requiring PDF Compression
• Prerequisites
• Practical PDF Compression Techniques in Python
  • Font Compression and Unembedding
  • Image Compression
  • Full Document Compression
  • Removing Metadata and Attachments
  • Batch Compressing Multiple PDFs
• Summary

Common Scenarios Requiring PDF Compression

Reducing the size of PDF documents is often essential in the following situations:

Prerequisites

Before you begin compressing PDFs with Python, make sure the following requirements are met:

• Python 3.7 or above
  Ensure that Python (version 3.7 or later) is installed on your system. You can download it from the official Python website.
• Spire.PDF for Python
  This is a powerful PDF library that allows you to programmatically create, manipulate, and compress PDF documents—without relying on external software like Adobe Acrobat.

To install Spire.PDF for Python, run the following command in your terminal or command prompt:

pip install spire.pdf

Need help with the installation? See our step-by-step guide: How to Install Spire.PDF for Python on Windows_

Practical PDF Compression Techniques in Python

In this section, you'll explore five practical techniques for reducing PDF file size:

• Font compression and unembedding
• Image compression
• Full-document compression
• Metadata and attachment removal
• Batch compressing multiple PDFs

Font Compression and Unembedding

Fonts embedded in a PDF—especially those from large font libraries or multilingual character sets—can significantly increase the file size. Spire.PDF allows you to:

• Compress embedded fonts to minimize space usage
• Unembed fonts that are not essential for rendering

from spire.pdf import *

# Create a PdfCompressor object and load the PDF file
compressor = PdfCompressor("C:/Users/Administrator/Documents/Example.pdf")

# Get the OptimizationOptions object
compression_options = compressor.OptimizationOptions

# Enable font compression
compression_options.SetIsCompressFonts(True)

# Optional: unembed fonts to further reduce size
# compression_options.SetIsUnembedFonts(True)

# Compress the PDF and save the result
compressor.CompressToFile("CompressFonts.pdf")

Image Compression

Spire.PDF lets you reduce the size of all images in a PDF by creating a PdfCompressor instance, enabling the image resizing and compression options, and specifying the image quality level. This approach applies compression uniformly across the entire document.

from spire.pdf import *

# Create a PdfCompressor object and load the PDF file
compressor = PdfCompressor("C:/Users/Administrator/Documents/Example.pdf")

# Get the OptimizationOptions object
compression_options = compressor.OptimizationOptions

# Enable image resizing
compression_options.SetResizeImages(True)

# Enable image compression
compression_options.SetIsCompressImage(True)

# Set image quality (available options: Low, Medium, High)
compression_options.SetImageQuality(ImageQuality.Medium)

# Compress and save the PDF file
compressor.CompressToFile("Compressed.pdf")

Full Document Compression

Beyond optimizing individual elements, Spire.PDF also supports full-document compression. By adjusting the document's CompressionLevel and disabling incremental updates, you can apply comprehensive optimization to reduce overall file size.

from spire.pdf import *

# Create a PdfDocument object
pdf = PdfDocument()

# Load the PDF file
pdf.LoadFromFile("C:/Users/Administrator/Documents/Example.pdf")

# Disable incremental update
pdf.FileInfo.IncrementalUpdate = False

# Set the compression level to the highest
pdf.CompressionLevel = PdfCompressionLevel.Best

# Save the optimized PDF
pdf.SaveToFile("OptimizeDocumentContent.pdf")
pdf.Close()

Removing Metadata and Attachments

Cleaning up metadata and removing embedded attachments is a quick way to reduce PDF size. Spire.PDF lets you remove unnecessary information like author/title fields and attached files:

from spire.pdf import *

# Load the PDF
pdf = PdfDocument()
pdf.LoadFromFile("Example.pdf")

# Disable the incremental update
pdf.FileInfo.IncrementalUpdate = False

# Remove metadata
pdf.DocumentInformation.Author = ""
pdf.DocumentInformation.Title = ""

# Remove attachments
pdf.Attachments.Clear()

# Save the optimized PDF
pdf.SaveToFile("Cleaned.pdf")
pdf.Close()

Batch Compressing Multiple PDFs

You can compress multiple PDFs at once by looping through files in a folder and applying the same optimization settings:

import os
from spire.pdf import *

# Folder containing the PDF files to compress
input_folder = "C:/PDFs/" 

# Loop through all files in the input folder
for file in os.listdir(input_folder):
    # Process only PDF files
    if file.endswith(".pdf"):  
        # Create a PdfCompressor instance and load the file
        compressor = PdfCompressor(os.path.join(input_folder, file))
        
        # Access compression options
        opt = compressor.OptimizationOptions        
        # Enable image resizing
        opt.SetResizeImages(True)        
        # Enable image compression
        opt.SetIsCompressImage(True)        
        # Set image quality to medium (options: Low, Medium, High)
        opt.SetImageQuality(ImageQuality.Medium)
        
        # Define output file path with "compressed_" prefix
        output_path = os.path.join(input_folder, "compressed_" + file)        
        # Perform compression and save the result
        compressor.CompressToFile(output_path)

Summary

Reducing the size of PDF files is a practical step toward faster workflows, especially when dealing with email sharing, web uploads, and large-scale archiving. With Spire.PDF for Python, developers can implement smart compression techniques—ranging from optimizing images and fonts to stripping unnecessary elements like metadata and attachments.

Whether you're building automation scripts, integrating PDF handling into backend services, or preparing documents for long-term storage, these tools give you the flexibility to control file size without losing visual quality. By combining multiple strategies—like full-document compression and batch processing—you can keep your PDFs lightweight, efficient, and ready for distribution across platforms.

Want to explore more ways to work with PDFs in Python? Explore the full range of Spire.PDF for Python tutorials to learn how to merge/split PDFs, convert PDF to PDF/A, add password protection, and more.

Frequently Asked Questions

Q1: Can I use Spire.PDF for Python on Linux or macOS?

A1: Yes. Spire.PDF for Python is compatible with Windows, Linux, and macOS.

Q2: Is Spire.PDF for Python free?

A2: Spire.PDF for Python offers a free version suitable for small-scale and non-commercial use. For full functionality, including unrestricted use in commercial applications, a commercial version is available. You can request a free 30-day trial license to explore all its premium features.

Q3: Will compressing the PDF reduce the visual quality?

A3: Not necessarily. Spire.PDF’s compression methods are designed to preserve visual fidelity while optimizing file size. You can fine-tune image quality or leave it to the default settings.