The fastest way to shrink a PDF depends on what's inside it

A PDF file gets large when it contains high-resolution images, embedded fonts, or uncompressed data. You can reduce file size by removing or compressing those elements — but the method you choose depends on whether you need the PDF to look identical or just readable.

If the PDF is mostly text with a few images, you can often cut the file size in half or more. If it's a scanned document or contains photos, you'll get smaller results but the file will still shrink noticeably. The trade-off is always the same: smaller file size means lower image quality, so you need to decide what quality you actually need before you start.

Key Takeaways

  • Most PDFs shrink by 30 to 70 percent when you compress the images inside them, which is the fastest method for most files.
  • Built-in tools on Windows and Mac can compress PDFs without installing new software, though they offer fewer options than dedicated programs.
  • Online PDF compressors work quickly but upload your file to someone else's server, so avoid them if the PDF contains sensitive information.
  • Scanned documents and image-heavy PDFs compress more than text-based ones, because images take up far more space than words.
  • You can always test compression at a low setting first, read the result, and try again if it's still too large.

Using built-in tools on your computer

On Mac: Open the PDF in Preview (the default PDF viewer). Go to File, then click Export. In the dialog that opens, change the Quartz Filter dropdown from "None" to "Reduce File Size". Click Save. This compresses images automatically and usually cuts file size by 30 to 50 percent. The quality loss is usually minor for documents you plan to read on screen or print at normal size.

On Windows: Open the PDF in Microsoft Edge (built into Windows 10 and later). Click the three dots in the top right, select Print, then choose "Microsoft Print to PDF" as the printer. In the printer settings, look for options like "Quality" or "Print Quality" and set it to "Draft" or "Standard" instead of "Best". Click Print and save the new file. This method works but gives you less control than Mac's Preview tool.

Both methods are free and don't require uploading your file anywhere. The downside is you get limited control over how much compression happens — you either compress or you don't.

Using dedicated PDF compression software

If the built-in tools don't shrink your file enough, or if you need more control over the compression settings, dedicated software gives you options. Adobe Acrobat Reader (the free version) cannot compress PDFs, but Adobe Acrobat Pro (paid subscription, around $15 per month) includes a "Reduce File Size" tool that lets you choose compression levels and see the result before saving.

ILovePDF and Smallpdf are online tools that compress PDFs in your browser. You upload the file, choose compression strength (usually "Low", "Medium", or "High"), and read the result. Both are free for a limited number of files per month. The risk is that your PDF travels to their servers, so don't use these tools if the document contains passwords, financial information, or anything you wouldn't want stored temporarily on someone else's computer.

Ghostscript is free, open-source software that compresses PDFs from the command line — it's powerful but requires typing commands rather than clicking buttons. It's best for people comfortable with technical tools or who need to compress many PDFs at once.

Compression settings and what they mean

When you have options, you'll usually see settings like "Low", "Medium", or "High" compression, or sometimes a quality slider from 1 to 100. Lower compression (or higher quality numbers) means the file stays larger but looks better. Higher compression means the file shrinks more but images become blurry or pixelated.

For documents you'll only read on screen or email to someone, "Medium" or "High" compression usually works fine — the difference is hard to see at normal viewing size. For documents you plan to print, or that contain important details like charts or small text, use "Low" or "Medium" compression so the text stays sharp.

The best approach is to compress at a medium setting first, read the file, and open it to check. If it looks acceptable, you're done. If it's still too large or looks worse than you need, try again with a higher compression setting.

When compression won't help much

Some PDFs are already compressed or contain very little that can be compressed further. A PDF that's mostly text with no images will shrink only 5 to 15 percent, because text takes up very little space. A PDF that's already been compressed once won't compress much a second time.

If you have a PDF that's a scanned image of a document (rather than a document that was converted to PDF), you can compress it more aggressively because the entire file is essentially a photograph. Scanned PDFs often shrink by 50 to 70 percent without major quality loss, because the original scan is usually higher resolution than necessary.

Removing pages or elements to make a PDF smaller

If compression alone doesn't get the file small enough, you can remove content. Most PDF readers let you delete pages — in Preview on Mac, right-click a page in the sidebar and select Delete. In Adobe Acrobat Reader (free version), you cannot delete pages, but Acrobat Pro can.

You can also remove images from a PDF if they're not essential. This requires more technical work — you'd need to open the PDF in editing software like Adobe Acrobat Pro or use an online tool that lets you select and delete images. For most people, compression first and deletion second is the right order.

Comparing file sizes before and after

Before you compress, right-click the PDF file and select Properties (Windows) or Get Info (Mac) to see the current file size in megabytes or kilobytes. After compression, check the new file's size the same way. This tells you whether the compression actually helped and by how much.

A file that shrinks from 50 MB to 15 MB is a good result. A file that shrinks from 5 MB to 4.5 MB probably isn't worth the quality loss. Keep the original file in case you need it later — compression is not reversible, so if the compressed version doesn't work for your purpose, you'll need the original.

Frequently Asked Questions

Can I compress a PDF multiple times to make it even smaller?

You can, but each compression pass loses more quality and produces smaller gains. Compressing a second time usually shrinks the file by only 5 to 10 percent more, while the quality drops noticeably. It's better to compress once at the right setting than to compress multiple times.

Will compression make text blurry or hard to read?

Compression affects images more than text. If your PDF is mostly words, compression usually won't blur the text noticeably. If it contains charts, photographs, or scanned pages, medium to high compression can make those elements look softer or less sharp. Test at a medium setting first to see if it's acceptable for your use.

Is it safe to use online PDF compressors?

Online tools are convenient but your file uploads to their server. If the PDF contains sensitive information — financial records, medical details, passwords — use a tool on your own computer instead. For general documents like resumes or articles, online compressors are usually fine.

What's the smallest a PDF can get?

That depends entirely on what's inside it. A text-only PDF might shrink only 10 to 15 percent. A scanned document or image-heavy PDF can shrink 50 to 70 percent. There's no universal minimum — you compress until the file is small enough for your purpose and the quality is acceptable.

Should I compress before or after sending a PDF to someone?

Compress before sending if file size is the reason you're compressing — smaller files email faster and take up less space in someone's inbox. If you're compressing for storage on your own computer, timing doesn't matter. Always keep the original uncompressed file in case you need it later.