The fastest way to shrink a PDF

The quickest method depends on what device you're using and what created the PDF in the first place. If you made the PDF yourself from a document or image, re-exporting it at lower quality settings usually cuts the file size in half or more. If someone sent you a PDF, using an online compression tool takes about two minutes and requires no software installation.

On Windows, Mac, or Linux, you can also use free desktop software like Ghostscript or ImageMagick to compress PDFs in bulk. These tools are more powerful than online converters but require a bit of setup. For most people, an online tool or your original software is the practical choice.

Key Takeaways

  • Re-exporting a PDF from its source file (Word, PowerPoint, Photoshop) at lower quality settings usually shrinks it more than any compression tool can.
  • Online PDF compressors like Smallpdf, ILovePDF, and PDF Compressor work on any device and typically reduce file size by 20 to 50 percent without visible quality loss.
  • Removing images, embedded fonts, or metadata from a PDF requires desktop software like Ghostscript or a paid PDF editor, but can shrink very large files significantly.
  • Scanned PDFs (photos of documents) compress better with image compression than with PDF-specific tools, because they're stored as images inside the PDF.

Re-export from the original file if you created the PDF

If you made the PDF from Word, PowerPoint, Google Docs, or another program, opening the original file and exporting again at lower settings is almost always faster and more effective than compressing afterward. The original software gives you direct control over image quality, which is what takes up most of the space.

In Microsoft Word, go to File → Save As, choose PDF, then click Options. Check the box for Optimize for File Size or set image quality to Medium or Low. In PowerPoint, the same option appears under File → Export as PDF. Google Docs doesn't have quality settings, but you can download as PDF and then compress it with an online tool.

If you created the PDF from images in Photoshop or another image editor, export at 72 DPI (dots per inch) instead of 300 DPI, and use JPEG compression instead of PNG. This alone can reduce file size by 80 percent or more. For scanned documents, 150 DPI is usually enough for reading; you don't need the 300 DPI that scanners default to.

Use an online PDF compressor for files you received

If someone sent you a PDF or you can't access the original file, an online compression tool is the simplest option. Smallpdf, ILovePDF, and PDF Compressor are three widely used free services. You upload the PDF, choose a compression level (usually "low loss" or "high compression"), and download the result. Most take 30 seconds to a few minutes.

These tools work by reducing image quality inside the PDF and removing unnecessary data that the PDF format stores but doesn't display. They typically shrink files by 20 to 50 percent. The quality loss is usually invisible for documents with text and simple graphics, but noticeable if the PDF contains photographs or detailed artwork.

One important note: uploading to an online service means the file leaves your computer. If the PDF contains sensitive information, use a desktop tool instead, or check the service's privacy policy. Most reputable compressors delete files from their servers within a few hours, but you're trusting them to do so.

Remove images and fonts with desktop software

For very large PDFs or files that contain embedded fonts and metadata you don't need, desktop software gives you more control. Ghostscript is free and works on Windows, Mac, and Linux. It's a command-line tool, which means you type instructions rather than clicking buttons, but it's powerful enough to compress PDFs that online tools can't handle.

To use Ghostscript, you download and install it, then open a terminal or command prompt and run a command like this: gswin64c -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf. The -dPDFSETTINGS=/ebook part controls quality; you can also use /screen for lower quality or /prepress for higher quality.

ImageMagick is another free option that works similarly. Paid PDF editors like Adobe Acrobat Pro and PDFtk allow you to remove embedded fonts, delete pages, and strip metadata through a graphical interface, but cost money and are overkill for simple compression.

Compress scanned documents differently

Scanned PDFs—files created by photographing or scanning paper documents—are actually image files wrapped in a PDF container. Compressing them with a standard PDF tool often doesn't work well because the tool tries to preserve text quality. Instead, treat them as images.

Open the PDF in an image editor like GIMP (free) or Photoshop, reduce the DPI from 300 to 150 or 100, and re-export as a PDF. Alternatively, use an online image compressor on each page after converting the PDF to individual image files. This approach usually shrinks scanned documents by 60 to 80 percent while keeping them readable.

If the scanned PDF contains multiple pages, some online tools like ILovePDF have a specific "compress scanned PDF" option that applies image compression automatically. This is faster than converting pages individually.

What file size reduction to expect

How much smaller a PDF becomes depends on what's inside it. A text-only document with no images might shrink by only 10 to 20 percent because there's not much to compress. A document full of high-resolution photographs can shrink by 50 to 80 percent. Scanned documents usually compress by 60 to 80 percent because they're stored as uncompressed images.

If you re-export from the original file at lower quality settings, you'll see bigger reductions than using a compression tool on an already-exported PDF. This is because the original software has access to the raw images and can compress them from scratch. A compression tool can only work with what's already in the PDF.

There's a trade-off: the more you compress, the lower the quality. For documents you're archiving or sharing by email, "medium" compression is usually the right balance. For documents you need to print or read closely, use "low" compression or don't compress at all.

Frequently Asked Questions

Will compressing a PDF make it blurry or hard to read?

Not usually, if you use low or medium compression. Text stays sharp because PDFs store text as actual text, not as an image. Photographs and graphics may lose some detail, but the difference is often invisible on screen. If you're worried, compress a test copy first and check the quality before sharing the original.

Can I compress a PDF that's password-protected?

Online tools usually can't compress password-protected PDFs because they can't read the content. You'll need to remove the password first using a PDF editor, then compress. If you don't know the password, you'll need to contact whoever created the PDF.

What's the smallest a PDF can get?

There's no absolute minimum, but most PDFs stop shrinking after a certain point. A text-only document might only compress by 10 to 15 percent total. A photo-heavy document might compress by 70 to 80 percent. After that, further compression usually requires removing content (like deleting pages or images), not just changing settings.

Is it safe to use online PDF compressors?

Reputable services like Smallpdf and ILovePDF are generally safe—they use encryption and delete files after a few hours. However, if your PDF contains confidential information, using a desktop tool keeps the file on your computer. Check the service's privacy policy before uploading anything sensitive.

Can I compress multiple PDFs at once?

Most online tools compress one file at a time, though some offer batch processing if you pay for a subscription. Desktop tools like Ghostscript and ImageMagick can compress many files in one command, but require command-line knowledge. For a few files, compressing them one at a time online is usually faster than learning the software.