- PDF compressors side by side: type and compression control
- Ten PDF compression tools, A to Z
- Strong, extreme or maximum: why compression level names don't line up
- Resolution sliders, batch uploads and extra switches
- Compression engines for developers and document pipelines
- Questions to ask before you shrink a PDF
- My advice for choosing a PDF compressor
- Frequently asked questions
The best PDF compressor is the one that gives your file the amount of control it needs. Some tools offer three preset levels, some offer four, some add a custom image-quality setting, some take a batch of files at once, and one is an engine for developers. Read how each tool names its levels, because strong on one site isn't strong on another.
You've got a PDF that's too big to email or upload, and every site you try shows a different set of buttons. Low, medium, strong. Extreme, recommended, less. Minimum to maximum. It's easy to assume they all mean the same thing. They don't.
This list covers ten PDF compression tools, using only what each maker's own page says, read on 2 Nov 2026 (as of Nov 2026). It's alphabetical and in no particular order. It's about how much control each tool gives you over compression, and the size-saving claims on some of these pages aren't repeated here.
PDF compressors side by side: type and compression control
| Tool | Type | Good for |
|---|---|---|
| CleverPDF | Online PDF compressor | Four levels plus a custom image-quality setting |
| docuPub | Online PDF compression with presets | Four presets and Acrobat compatibility choices |
| FreeConvert | Online file converter and compressor | A compression level menu beside other compressors |
| Ghostscript | PDF conversion engine and SDK | Compression inside apps and server pipelines |
| iLovePDF | Online PDF toolbox with desktop apps | Extreme, recommended and less compression |
| PDF Compressor | Online batch PDF compressor | Up to 20 files at once, with a ZIP download |
| PDF24 | Online PDF tools with a desktop app | Adjustable resolution and image quality |
| PDFgear | Online PDF compressor with offline software | Low, medium and strong compression |
| Sejda | Online PDF tools with a desktop version | Compressing as one step in a wider PDF toolbox |
| Smallpdf | Online PDF toolbox with a mobile app | Compressing Office and image uploads as well as PDFs |
Ten PDF compression tools, A to Z
CleverPDF
Best for: Choosing a compression level, from Minimum up to Maximum, or customising image quality yourself when you shrink a PDF online.
docuPub
Best for: Reducing large PDF documents with four presets, from low to maximum compression, and a choice of Acrobat 4.0, 5.0 or 6.0 compatibility.
FreeConvert
Best for: Setting a compression level, from no compression up to high, on a site that also compresses GIFs and video.
Ghostscript
Best for: Building PDF compression into apps and server-side document pipelines, with full control over settings, rather than clicking a button on a website.
iLovePDF
Best for: Choosing between extreme, recommended and less compression, with merge, split and scan to PDF in the same toolbox.
PDF Compressor
Best for: Compressing up to 20 PDFs in one go, then downloading each file on its own or all of them together in a ZIP archive.
PDF24
Best for: Shrinking PDFs by reducing image resolution and quality and removing unneeded data, with each of those settings adjustable.
PDFgear
Best for: Picking low, medium or strong compression when you reduce a PDF's size online.
Sejda
Best for: Reducing a PDF's size from a toolbox that also edits, merges, crops, protects and unlocks PDFs.
Smallpdf
Best for: Compressing PDF, image, Word, Excel or PowerPoint uploads from a toolbox that also converts, merges, edits and signs.
Strong, extreme or maximum: why compression level names don't line up
Here's the part you won't guess from the buttons: PDF compressors name and group their compression levels differently, so the same word can mean different things on two sites.
PDFgear offers 'low compression', 'medium compression' and 'strong compression', and its page marks medium as the recommended choice. iLovePDF's three levels are 'extreme compression', 'recommended compression' and 'less compression'. CleverPDF has four, running from Minimum, which its page says leaves images alone and only optimises font and data, up to Maximum, with a 'customize image quality' setting on top.
docuPub has four presets too, from low compression to maximum compression, and adds a choice of Acrobat compatibility. FreeConvert's menu runs No Compression, Low, Medium and High, and its page describes High as maximum compression. Smallpdf's page names a Strong level of its own. So a strong file from one site and a high file from another aren't the same setting, and a middle level on one tool can sit at a different point on the next.
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- Three presets: a low, middle and high choice, with the middle one marked as recommended on two of the pages here.
- Four presets: levels that run from minimum or low up to maximum, and on one tool a no-compression option.
- A custom setting: an image-quality or resolution control you set yourself instead of picking a preset.
- An engine: a library you build into your own software, with full control over settings.
Resolution sliders, batch uploads and extra switches
Some tools hand you the controls directly. PDF24 says it shrinks PDF files 'by reducing image resolution and quality and removing unneeded data, all adjustable', and its page shows a DPI box, an image quality setting and extra options such as converting images to grayscale, removing bookmarks and stripping metadata.
Other tools are built for volume. PDF Compressor says 'you can upload up to 20 files', then lets you download each one or all of them in a ZIP archive. If you've got a folder of scanned documents rather than one big report, that's the line to look for.
And some put compression inside a bigger toolbox. Sejda lists compress beside edit, merge, crop, password protection and watermarks, and offers a desktop version if you'd rather work offline.
Compression engines for developers and document pipelines
Ghostscript is a different kind of tool: a developer engine and SDK for server-side pipelines and apps, not a button on a website. Its page pitches 'powerful PDF compression' with 'full control over settings', and lists server-side PDF generation pipelines and document archiving among its uses. Some of the web tools here cater to developers too: one links to code samples for building your own compression application, and others list an API.
Questions to ask before you shrink a PDF
- Is it one file or a batch, and how many files at once does the tool take?
- Do I want a preset, or my own image-quality or resolution setting?
- What does this tool call its strongest level, and what does its page say that level does to images?
- Does the file need to open in an older version of Acrobat?
- Will I compress in a browser, in a desktop app or inside my own software?
- Do I need to edit, merge or sign the file once it's smaller?
Do you make a PDF compressor? Tool makers can ask to be considered for a featured place on this list.
My advice for choosing a PDF compressor
Start with how much control you want. If you just need a smaller file for an email, a tool with three named presets keeps it simple, and two of the pages here mark the middle level as recommended, so that's a sensible first try. If the images in your file matter, pick a tool with a custom image-quality or resolution setting so you decide what gets squeezed. If you've got a pile of files, look for batch uploads. And if compression has to happen inside your own app or server, you want an engine, not a website. Whatever you use, read the level names on that site rather than assuming they match the last one you tried.
If the PDF started life as a Word file, my guide on how to convert Word to PDF covers that step. Need to change the content as well as the size? Here are the best PDF editors. And if it's a video that's too big rather than a document, I've rounded up video compressors too.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
Why do PDF compression levels have different names on different sites?
Because each maker names its own. On this list, one offers low, medium and strong, another offers extreme, recommended and less, and others run four levels from minimum or low up to maximum. Read what each level does on that site rather than matching names across tools.
Can I set image quality myself instead of using a preset?
Some tools let you. One here adds a customize image quality setting on top of its levels, and another lets you adjust image resolution and quality and turn extra options on or off. Others stick to presets, so check before you upload.
Which of these compress several PDFs at once?
One online tool here says you can upload up to 20 files and download them together in a ZIP archive. Another maker says its Windows desktop version supports batch processing. Check each tool's own page for how many files it takes.
Do any of these work offline or as a desktop app?
Several list one. Pages here mention a desktop app, a desktop version, offline software and a Windows desktop version alongside the online compressor. One more is an engine you download and build into your own software.
Can I compress Word or PowerPoint files too?
One tool on this list accepts PDF, image, Word, Excel and PowerPoint files on its compress page. The rest are built around PDFs, so check the supported formats on each compress page before you upload.
Can I keep a compressed PDF compatible with older versions of Acrobat?
One tool here lets you choose compatibility with Acrobat 4.0 and later, 5.0 and later or 6.0 and later when you compress. If an older reader matters to you, look for that setting before you start.
