How to Make a PDF Smaller: 5 Tested Ways for Free/High-Quality

Part 1. Why Is My PDF File so Large? 5 Hidden Reasons

Before learning how to make a PDF smaller, it helps to understand why your file has become so heavy. Here are the five main culprits behind oversized PDFs:

• High-resolution images: Uncompressed photos or scanned documents are the biggest reason for large PDF sizes.
• Embedded fonts: To ensure your document looks the same on all devices, PDFs often embed multiple font files, which increases the file size.
• Vector graphics: Complex charts, CAD drawings, or Illustrator files contain lots of path data, making the PDF much larger.
• Metadata and annotations: Bookmarks, comments, and highlights are useful but add extra weight to the file.
• Outdated PDF versions: Older PDF formats may include redundant data and are less optimized than newer versions.

Once you know what’s making your PDF so large, you can choose the most effective way to reduce its size.

Part 2. 5 Tested Methods to Make a PDF Smaller

I’ve carefully selected and tested five representative ways to make a PDF smaller - from all-in-one professional tools to lightweight online options. No matter your needs, there’s a perfect solution waiting for you.

1: Adobe Acrobat Pro – Professional Standard Tool

Adobe Acrobat Pro is widely regarded as the gold standard in the PDF world. It’s not just a document viewer - it’s a complete platform for editing, optimizing, and managing PDFs.

As the creator of the PDF format, Adobe has unmatched precision and expertise when it comes to decreasing PDF file size. Its built-in PDF Optimizer goes far beyond basic compression. It gives users full control over compression settings, offering a highly customizable and high-quality PDF size reducer that ensures clarity and efficiency at the same time.

User Guide

• Open your PDF in Adobe Acrobat Pro.
• Go to File > Save As Other > Reduced Size PDF. (On macOS, you may also find this under the File menu as Save As Other or in the Hamburger menu.)

• In the dialog box, select the compatibility version you need. For most modern uses, Acrobat 10.0 and later or Retain existing is a good choice.

• Click OK. When the "Save As" dialog appears, give your new, smaller file a different name to avoid overwriting the original. Click Save.
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Item
Details
Best For
Designers, publishing professionals, and advanced users who need full control over PDF compression.
Test Result
After processing a 120MB design file, the PDF was successfully compressed to 18MB while maintaining print-ready quality.
Key Advantage
Offers fully controllable, high-quality PDF compression with comprehensive features - the true industry standard.
Note
Expensive and complex for beginners. Not ideal for users who just want a quick way to make a PDF smaller.

2: Tenorshare PDNob – Secure, High-Quality Compression

Tenorshare PDNob is a powerful all-in-one desktop tool that does much more than just reduce PDF size. It’s a complete PDF workstation built for users who care about privacy, efficiency, and control.

Its biggest strength lies in offline PDF compression, which means your files never leave your computer. This ensures total data security - perfect for sensitive materials like contracts or financial reports. PDNob also supports batch compression, allowing you to shrink PDF size for dozens of files in just a few minutes.

In testing, a 35MB report was reduced to 4.1MB with no visible quality loss. Beyond compression, PDNob offers editing, format conversion, splitting, and merging features - a true one-stop solution for anyone who needs to make a PDF smaller quickly and safely.

User Guide

• Launch PDNob PDF Editor and load the PDF file you want to compress. Once it’s open, look at the top toolbar and click on the tools and then click the “Compress”.

  

• From the dropdown menu that appears, select “Compressed PDF”. This will open up a new window with several compression levels to choose from.

• You’ll see options like: High quality, Middle quality and Low quality.

  

  The lower the quality you pick, the smaller the final file size will be. Just keep in mind—more compression might take a few extra seconds.

• Once you’ve picked your compression level, hit the “Compress Button” button. Choose where to save the new file, give it a name, and click “Compress”. That’s it! Your PDF is now lean and ready to go.

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3: iLovePDF – Fast and Easy Online Compressor

iLovePDF is one of the most popular free PDF compression tools, known for its simplicity and no-registration-needed workflow. Its main advantage is speed, making it ideal for temporary use or non-sensitive documents. Users can shrink PDF size in just a few clicks: upload the file, choose a compression level, and download the compressed PDF in seconds. The process is extremely quick and easy.

User Guide

• Visit the iLovePDF website, click “Compress PDF”, and upload the PDF you want to compress.

• Choose a compression mode: Recommended Compression, Extreme Compression, or Less Compression.
• Click “Compress PDF” and wait a few seconds - the compressed file will be ready to download.
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Item
Details
Best For
Casual users who need to quickly compress files.
Test Result
Compressed a photo collection for friends using Recommended Compression - clarity preserved, file size significantly reduced.
Key Advantages
Completely free, extremely simple, ideal for quick PDF compression.
Note
Not suitable for sensitive files; compression speed depends on internet connection.

4: Smallpdf – Reliable Online PDF Size Reducer

Smallpdf is a major competitor to iLovePDF, praised for its modern interface and higher stability. It’s also a free PDF compression tool, but with extra attention to detail. Smallpdf promises that all uploaded files are deleted from their servers within one hour, providing an extra layer of privacy for users.

In practice, Smallpdf’s Basic Compression mode often strikes a better balance than iLovePDF, slightly outperforming in reducing file size while preserving clarity. For users with higher demands, the Strong Compression (Pro feature) can further shrink PDF size - ideal for extreme compression scenarios.

However, the free version has daily limits (usually 2 tasks per day); beyond that, users must wait or upgrade to Pro. This makes it suitable for occasional use rather than frequent batch compression.

User Guide

• Go to the Smallpdf website, click the “Compress PDF” shortcut, and upload your file.

• Choose a compression mode: Basic Compression or Strong Compression.
• Wait for the process to complete, then click Save to download your compressed PDF.
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Item
Details
Best For
Users who prefer a clean interface and occasional online PDF compression.
Test Result
In tests with the same file, Smallpdf’s Basic Compression balanced quality and file size better than iLovePDF.
Key Advantages
Modern interface, stable compression results, files are automatically deleted for privacy.
Note
Free version allows only 2 tasks per day; not suitable for batch or frequent use.

5: Preview – Free Built-In Option for Mac Users

Many Mac users don’t realize that the macOS Preview app includes a built-in PDF compression feature. Using Quartz filters, it can shrink PDF size for free without installing any additional software. For text-heavy documents, Preview often delivers excellent results with minimal impact on readability.

I frequently use it for lecture notes, company documents, and other text-based PDFs. For example, a 10MB text-only file can be compressed to under 2MB effortlessly. The process is extremely simple - just select the “Reduce File Size” filter when exporting.

However, there are some limitations. Compression is all-or-nothing, with no customization options. PDFs containing many images may lose clarity, making photos appear blurry. Therefore, Preview is best suited as a quick PDF compression method for Mac users who prioritize speed and convenience over fine control.

User Guide

• Open the PDF you want to compress in Preview.
• Go to the menu bar and select File > Export.
• In the export dialog box, click the Quartz Filter dropdown menu. From the list, select "Reduce File Size".

• You can optionally rename the file in the "Export As" field to avoid overwriting the original.
• Click Save to create the smaller PDF.

• If you are asked to replace the original file, click Save again to confirm, or click Cancel to choose a different filename first.
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Item
Details
Best For
All Mac users, especially those who only need simple PDF compression for text documents.
Test Result
Works very well for text-based PDFs, but image quality can drop significantly - not ideal for image-heavy files.
Key Advantages
Built into macOS, completely free, very easy to use.
Note
Compression quality cannot be controlled; images may be heavily affected.

Part 3. Which PDF Size Reducer Should You Choose?

The table below compares the key advantages, security, pricing, and recommended use cases for each tool.

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Part 4. Common Questions About How to Make a PDF Smaller

Q1: What should I do if my PDF is too large to upload to a school system?

Most school systems have a 10MB file limit. For high-quality compression, Tenorshare PDNob can easily reduce your file to meet the requirement. If you’re a Mac user and the PDF is mostly text, the Preview App is a free and effective option.

Q2: How can I compress a PDF to the smallest size (e.g., under 1MB)?

For extreme compression, use iLovePDF or Smallpdf and select Strong/Extreme Compression, or manually reduce image DPI to 72 in Adobe Acrobat Pro. Keep in mind that such compression will significantly reduce image quality.

Q3: With so many options, which tool should I use?

• Security and regular use: Choose Tenorshare PDNob.
• Mac users with text-only files: Try the Preview App.
• Temporary or non-sensitive tasks: Use iLovePDF or Smallpdf.
• Professionals with budget: Go for Adobe Acrobat Pro.

Part 5. Conclusion

From this in-depth comparison, it’s clear that there’s no single best way to make a PDF smaller - only the method that fits your needs.

• For most users seeking efficiency, security, and high-quality compression - whether students or professionals - Tenorshare PDNob provides the best all-around experience.
• For occasional or temporary needs, online tools like iLovePDF and Smallpdf remain convenient and effective options.
• Mac users can take full advantage of the built-in Preview App to meet basic compression needs without spending money or installing extra software.

This ultimate guide, covering five tested methods, will help you confidently tackle the PDF file too large problem and choose the right tool for any situation.

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