PDF Compressor Free: 10 Best Tools to Reduce PDF Size in 2026

Looking for a pdf compressor free tool that actually works? You are not alone. Whether you need to shrink a PDF for email, squeeze it under an upload limit, or clear storage on your hard drive, a reliable free PDF compressor saves time and frustration every single day.

The problem is that dozens of tools claim to compress PDFs for free, but many come with hidden limits — file size caps, watermarks, daily quotas, or aggressive upsells. This guide cuts through the noise and covers the genuinely best free options available in 2026, split into online tools and desktop applications, so you can pick the right one for your workflow.

Best Free Online PDF Compressors

Online tools are the fastest way to compress a PDF when you need a quick result and don't want to install anything. Here are the top four free online options.

1. iLovePDF

iLovePDF is one of the most popular free PDF compression tools on the web, and for good reason. It offers three compression levels — extreme, recommended, and less compression — so you can balance file size against quality.

What makes it stand out:

• No file size limit on the free tier
• Batch compression (up to 2 files free, unlimited with premium)
• Clean interface with no confusing options
• Files are deleted from servers after two hours

The free tier limits you to two files per task, but for single-file compression it is completely unrestricted. Results are solid: a 15 MB scan-heavy PDF typically drops to 3-5 MB on the recommended setting.

2. PDF24

PDF24 is a fully free PDF compressor with no daily limits, no watermarks, and no registration required. It is run by a German company and has been around since 2006, which gives it more credibility than most free tools.

What makes it stand out:

• Truly unlimited free compression with no caps
• Multiple quality presets (DPI-based control)
• No account or sign-up required
• GDPR-compliant with automatic file deletion

PDF24 also offers a free desktop app for Windows, making it a strong choice if you want both online and offline options. The compression quality is excellent, especially at the 144 DPI setting which preserves readability for most documents.

3. Smallpdf

Smallpdf offers a polished, intuitive interface that makes PDF compression feel effortless. The free tier allows two tasks per day, which is enough for occasional use but can feel restrictive if you compress files regularly.

What makes it stand out:

• Drag-and-drop interface with instant results
• Basic and strong compression modes
• Integration with Google Drive and Dropbox
• Preview before downloading

The two-task daily limit is the main drawback. If you need to compress more than two PDFs a day, you will hit a paywall. But for light usage, Smallpdf consistently delivers clean compression with minimal quality loss.

4. Adobe Acrobat Online

Adobe's online PDF compressor carries the weight of the Acrobat brand, and the results are predictably good. The free tier lets you compress one file at a time with three compression levels.

What makes it stand out:

• Backed by Adobe's industry-leading PDF technology
• Three compression levels (high, medium, low)
• Reliable quality preservation even at high compression
• Seamless integration with Adobe ecosystem

The biggest limitation is speed — Adobe's online tool can be slower than competitors, and the free tier is restrictive. But if quality is your top priority and you only need to compress one or two files, it is hard to beat Adobe's engine.

For a deeper dive into compression methods, check out our guide on how to compress PDF file size effectively.

Best Free Desktop PDF Compressors

Desktop tools keep your files offline, offer faster processing for large documents, and typically have no daily usage limits. Here are the best free desktop options for compressing PDFs.

5. Preview (Mac — Built-in)

Every Mac ships with Preview, and most users have no idea it can compress PDFs. This is the fastest free pdf compressor available to Mac users because there is nothing to download or configure.

What makes it stand out:

• Pre-installed on every Mac — zero setup
• Works completely offline
• No file size limits or daily caps
• Simple enough for anyone to use

The trade-off is limited control. Preview's default "Reduce File Size" filter can be aggressive, sometimes over-compressing images. For more nuanced compression, you can create custom Quartz filters (covered below). For a complete walkthrough, see our guide on how to compress PDF on Mac for free.

6. PDFgear

PDFgear is a free desktop PDF editor for Windows and Mac that includes a built-in compression tool. It doesn't require an account or subscription, and there are no hidden feature gates.

What makes it stand out:

• Completely free with no premium tier
• Available on Windows, Mac, and iOS
• Includes PDF editing, annotation, and conversion tools
• Decent compression ratios (40-60% reduction typical)

PDFgear is best for users who want an all-in-one PDF tool rather than just a compressor. The compression feature is solid but not as refined as dedicated tools — you get less control over quality settings compared to PDF24 or Compresto.

7. SwifDoo PDF (Windows)

SwifDoo PDF is a lightweight Windows application that handles PDF compression alongside editing and conversion. The free version includes compression with some limitations on advanced features.

What makes it stand out:

• Fast compression engine
• Batch processing in the free tier
• Small application footprint
• Multiple output quality presets

SwifDoo is Windows-only, which limits its audience, but for Windows users it provides a capable free pdf compressor without requiring an internet connection.

8. Compresto (Mac — Best Overall)

While not entirely free, Compresto deserves mention because it offers a free trial and solves every limitation of the free tools above. Built natively for macOS with hardware acceleration, Compresto compresses PDFs faster than any other tool on this list.

Why it's worth considering:

• Native macOS app with Apple Silicon optimization
• Hardware-accelerated GPU compression — large PDFs finish in seconds
• Batch processing for entire folders
• Adjustable quality slider with live file size preview
• Also handles video and image compression in one app

If you regularly compress PDFs and want the best results on Mac, Compresto replaces multiple tools with a single, fast application. Learn more about how it compares in our best PDF compressor software for Mac roundup.

How to Compress PDF on Mac for Free Using Preview

Preview is the hidden gem of free PDF compression on macOS. Here is a step-by-step walkthrough.

Basic Method

1. Open your PDF in Preview (right-click the file and select Open With > Preview)
2. Go to File > Export from the menu bar
3. In the Quartz Filter dropdown, select Reduce File Size
4. Choose your save location and click Save

This method typically reduces file size by 30-50%, though results vary depending on the content. Image-heavy PDFs see the biggest reductions.

Advanced Method: Custom Quartz Filters

Preview's default compression can be too aggressive for some documents. To get better control:

1. Open ColorSync Utility (search for it in Spotlight)
2. Click the Filters tab
3. Find Reduce File Size and duplicate it
4. Adjust the Image Compression quality slider and DPI settings
5. Save your custom filter — it will now appear in Preview's Quartz Filter dropdown

This gives you granular control over compression quality without installing any third-party software. For even more Mac-specific tips, read our complete guide to compressing PDFs on Mac for free.

How to Compress PDF Without Losing Quality

Quality loss is the biggest concern when compressing PDFs. Here is how to minimize it regardless of which tool you use.

Choose Lossless Over Lossy When Possible

Lossless compression restructures internal PDF data — removing duplicate objects, optimizing font subsets, and cleaning metadata — without touching the actual content. Most free tools offer a "low compression" or "less compression" mode that prioritizes quality.

Set the Right DPI for Your Use Case

DPI (dots per inch) directly affects image quality inside your PDF:

• 300 DPI — print-quality, largest file size
• 150 DPI — good for on-screen reading and most sharing
• 72 DPI — web-only, smallest file size but noticeable quality drop

If your PDF is destined for screen viewing or email, 150 DPI gives the best balance. Only drop to 72 DPI if file size is more important than image clarity.

Compress Images Before Embedding

If you are creating a PDF from scratch, compress images before adding them to the document. A 5000x3000 pixel photo destined for a quarter-page placement does not need to be full resolution. Resize and compress images first, then build your PDF — the result will be dramatically smaller with zero visible quality loss.

Avoid Multiple Compression Passes

Compressing a PDF that has already been compressed can degrade quality without meaningful size reduction. Each lossy pass removes more data. Compress once with the right settings rather than running a file through multiple tools.

For a comprehensive look at quality preservation techniques, see our guide on how to reduce PDF file size without destroying your documents.

PDF Compression Tips and Tricks

These practical tips help you get better results from any free pdf compressor tool.

Remove Unnecessary Elements Before Compressing

Before you compress, clean up your PDF:

• Delete blank pages that add weight without content
• Flatten form fields if the PDF no longer needs to be editable
• Remove annotations and comments from finalized documents
• Strip embedded multimedia (audio, video) if not needed

A clean PDF compresses more efficiently and produces a smaller final file.

Use the Right Tool for the Right Job

Not every PDF needs the same tool:

• Quick one-off compression — use an online tool like iLovePDF or PDF24
• Sensitive or confidential documents — use a desktop tool like Preview or Compresto
• Batch processing multiple files — use Compresto or PDF24 Desktop
• Maximum compression regardless of quality — use Smallpdf's strong compression mode

Understand What Makes PDFs Large

Knowing why your PDF is big helps you choose the right approach:

• Scanned documents — mostly images, compress well with lossy compression
• Text-heavy reports — already small, lossless compression is sufficient
• Design files from InDesign or Illustrator — embedded fonts and vectors, flatten layers before compressing
• Slide decks exported to PDF — high-res background images, reduce DPI

For a step-by-step tutorial on shrinking any type of PDF, check out our guide on how to compress a PDF file.

Monitor Compression Results

Always open the compressed PDF and check:

• Text readability — can you read all body text and footnotes?
• Image clarity — are charts, graphs, and photos still clear?
• Layout integrity — do pages, margins, and formatting look correct?
• Interactive elements — do links, bookmarks, and table of contents still work?

If anything looks wrong, re-compress with a lighter setting. A slightly larger file that looks perfect is always better than a tiny file that looks broken.

Frequently Asked Questions

What is the best pdf compressor free tool?

For online use, iLovePDF and PDF24 offer unlimited free compression with no file size caps. For Mac users, Preview is built in and handles basic compression well. For the best balance of speed, quality, and batch processing, Compresto is the top desktop choice.

Can I compress a PDF without losing quality?

Yes. Use lossless compression settings that restructure internal data without touching image resolution. Tools like PDF24 and Compresto let you choose compression levels so you control the quality-to-size tradeoff.

Is it safe to compress PDFs online?

Reputable tools like iLovePDF, Smallpdf, and PDF24 delete uploaded files within one to two hours. However, if your PDF contains sensitive or confidential data, use a desktop tool like Preview or Compresto to keep files entirely offline.

How much can a free PDF compressor reduce file size?

Most free PDF compressors reduce file size by 30-80% depending on the content. Image-heavy PDFs see the biggest reductions, while text-only documents may only shrink by 10-20%.

How do I compress a PDF on Mac for free?

Open the PDF in Preview, go to File > Export, select PDF from the format dropdown, choose the Quartz Filter "Reduce File Size," and click Save. This uses macOS built-in compression at no cost. For more control, create custom Quartz filters via ColorSync Utility.

Start Compressing Your PDFs Today

Free PDF compressors have come a long way. Online tools like iLovePDF and PDF24 handle casual compression needs without any setup, while desktop tools like Preview give Mac users a built-in solution.

But if you compress PDFs regularly — or if you also work with images and videos — a dedicated tool makes a real difference. Compresto combines hardware-accelerated PDF compression with image and video compression in a single native Mac app, delivering faster results and better quality than any free tool on this list.

Try Compresto free and see the difference a purpose-built compression tool makes.