How to Compress a PDF in Adobe Acrobat and Adobe Reader

No, not for free. Adobe Acrobat Reader is the free app for viewing, commenting on, filling in and signing PDFs. Compression isn't included, so choosing it in Reader prompts you to upgrade. In the Acrobat Reader mobile app, Compress PDF is also a premium feature that needs a subscription.

Adobe gives you three ways around this. You can pay for an Acrobat plan, which compresses PDFs on your computer. You can use Adobe's free online compressor, which has a usage limit. Or you can use a different free tool.

In current versions of Acrobat for Windows and Mac, compression lives in the Compress a PDF tool. Acrobat picks the settings for you and saves a smaller copy. Adobe says the desktop app keeps the file on your device rather than uploading it.

Reduced size PDF is the older route to the same result, and it is still in the menus. Acrobat 9 called it Document > Reduce File Size, so you may see that name in older guides. It uses preset settings that lower image resolution while trying to keep the document readable. The only choice you make is which Acrobat version the file must stay compatible with.

The PDF Optimizer, which Adobe now labels Advanced Optimization, gives you control over what gets compressed and by how much. Adobe says it is only available in Acrobat Pro, Premium or Studio on the desktop, not in Acrobat Standard or Reader.

Open it from the Compress a PDF panel, or with Menu > Save as Other > Optimized PDF. On a Mac, the path is File > Save as Other > Optimized PDF. Use the Audit space usage button in the Optimizer first. It lists how many bytes images, fonts, bookmarks and other parts use, so you can see what is making the file large before you change anything.

Adobe also has a compressor on its website, and you don't need Acrobat installed. Go to the Compress PDF page on adobe.com, or in Acrobat on the web choose Convert > Compress a PDF. Select the file, pick High, Medium or Low compression and select Compress.

Adobe says the online tool is free with limited use, and that unlimited compression, batch processing and advanced settings need a paid plan. It doesn't publish the exact free allowance. Files can be up to 2 GB. Your PDF is uploaded to Adobe's servers for processing. Adobe says the file is then deleted from its servers, and you only sign in if you want to save the result. For contracts, ID scans or medical records, a tool that never uploads the file avoids that step.

Which Adobe option you can use depends on your plan. All of them save a new copy and leave the original alone, so compare the two before deleting anything.

If you only have Reader, PDFToolz Compress PDF does the same job in your browser at no cost, with no account and no usage limit. The file is processed on your device and never uploaded, so it works for private documents too. It has three levels, and it never hands back a file bigger than the one you started with.

If an upload form or email sets a limit, such as 200 KB or 1 MB, use PDFToolz Compress PDF to Size. Enter the target and the tool searches for the best quality that fits. It tries settings that keep text selectable first, and only turns pages into images if nothing else fits. If no setting gets under the target, it says so and gives you the smallest file it could make.

Compression mostly works on images. A PDF made of text and vector drawings, such as a report exported from Word, is usually small already and has little left to remove. Running it through any compressor saves only a few percent.

If the file is a scan or full of photos and still won't shrink enough, the pages are probably large, high-resolution images. Lower the image resolution further with Advanced Optimization, convert the pages to grayscale, or remove pages you don't need. Compressing an already compressed file again rarely helps, and each lossy pass lowers the image quality a bit more.