The fastest way depends on what's taking up space

A document gets large because of images, embedded fonts, or formatting that repeats across many pages. The quickest fix is usually to compress the images inside it — most documents over 10 MB are heavy on pictures. If you're working in Google Docs, Microsoft Word, or LibreOffice, each has a built-in compression tool that shrinks images to screen resolution rather than print resolution. For PDFs, you can use a free online tool or your operating system's built-in compression, though this matters less for privacy than knowing which tool you're using and whether it uploads your file to someone else's server.

Before you start, decide what "smaller" means for your situation. Are you trying to email the file, store it on a device with limited space, or upload it somewhere with a file-size limit? The method changes based on that answer. Compressing images works for almost any document type. Removing pages or converting to a different format works for some. Deleting formatting or embedded objects works for others.

Key Takeaways

  • Image compression is the fastest way to shrink most documents — built into Word, Google Docs, and LibreOffice, it usually cuts file size by half or more.
  • Compression tools that run on your computer (like your operating system's built-in options) keep your document private; online tools upload your file to someone else's server.
  • Removing pages, deleting unused fonts, and stripping formatting all work but usually save less space than image compression.
  • PDF files compress differently than editable documents — PDFs benefit from dedicated compression tools, while Word and Docs documents benefit from image compression within the editor.

Compress images in Word, Google Docs, or LibreOffice

This is the single most effective step for most documents. In Microsoft Word, right-click any image in the document and select "Compress Pictures". A dialog box appears with options: choose "E-mail" or "Screen" rather than "Print" to shrink the resolution. Word will compress all images in the document at once. The file usually shrinks by 50 to 80 percent if it was image-heavy to begin with.

In Google Docs, click an image, then click the three-dot menu icon that appears and select "Image options". Under "Compression", choose "Low quality" or "Medium quality" depending on whether you need the image to look sharp on screen. Google Docs compresses only the selected image, so you may need to repeat this for each one. In LibreOffice Writer, right-click an image and select "Compress". Choose your target resolution — "Screen" is fine for most uses — and explore.

All three tools keep the compression on your own computer. Your document never leaves your device. This matters if the document contains sensitive information — medical records, financial statements, or anything you wouldn't want uploaded to a cloud service.

Convert or compress a PDF file

PDFs don't compress the same way as editable documents because the images are already flattened into the file. You have two routes: use your operating system's built-in tools, or use an online PDF compressor.

On Windows, right-click the PDF file, select "Send to", and choose "Compressed (zipped) folder". This creates a smaller version without uploading anything. The compression is modest — usually 10 to 30 percent — because PDFs are already fairly compact. On Mac, open the PDF in Preview, go to File menu, select "Export", and under "Quartz Filter" choose "Reduce File Size". This compresses the PDF's images and fonts in place.

If the built-in tools don't shrink it enough, online PDF compressors like Smallpdf, ILovePDF, or PDF Compressor will do more aggressive compression. These tools upload your file to their servers, compress it, and let you read the result. They delete the file after a set time (usually 24 hours), but during that window your document exists on someone else's computer. Use this route only if the document contains nothing sensitive, or if you trust the service's privacy policy.

Remove pages, delete unused fonts, or strip formatting

If compression doesn't shrink the file enough, look for content you can remove. Delete blank pages, unused sections, or appendices you don't need. In Word and LibreOffice, you can also remove embedded fonts — go to File > Options (Word) or Tools > Options (LibreOffice), find the Fonts section, and uncheck "Embed fonts in the file". This saves space only if the document uses unusual fonts; standard fonts like Arial or Times New Roman are already on most computers.

Stripping formatting — removing bold, italics, colors, and custom styles — saves space but usually only 5 to 15 percent. It's worth doing only if you're trying to hit a very tight file-size limit and compression didn't work. Copy all the text, paste it into a plain-text editor like Notepad, then paste it back into your document as unformatted text. This is tedious and loses visual structure, so do it only as a last resort.

Choose between file formats

The format you save in affects file size. A Word document (.docx) is usually smaller than a PDF of the same content because PDFs embed fonts and flatten images. If you're trying to shrink a document and the recipient can open Word files, save as .docx instead of .pdf. If you need to send a PDF, create it from a compressed Word document rather than converting an already-large PDF.

Google Docs and LibreOffice documents (.odt) are also smaller than PDFs. If you're sharing with someone who can open them, they're a good middle ground between editability and file size. The trade-off is that not everyone has software to open them — Word and Google Docs can open .odt files, but older versions of Word cannot.

What to do if you're uploading to a website or service

Many websites have file-size limits — some allow only 5 MB, others allow 25 MB or more. Before you spend time compressing, check what the limit is. If your document is 8 MB and the limit is 10 MB, compression might not be necessary. If the limit is 5 MB, compress images first, then try removing pages if needed.

Some services also compress files automatically when you upload them. Google Drive, Dropbox, and OneDrive all compress PDFs and images after upload to save storage space. If you're uploading to one of these, the file size on your computer doesn't matter as much — the service will shrink it anyway. Check the service's documentation to see whether it compresses and what quality settings it uses.

Privacy considerations when choosing a compression method

The privacy difference between methods matters if your document is sensitive. Compressing images within Word, Google Docs, or LibreOffice keeps the file on your device — nothing is uploaded. Using your operating system's built-in compression (Windows zip, Mac Preview) also keeps everything local. Using an online PDF compressor uploads your file to a third-party server, even if only temporarily.

If the document contains medical information, financial data, or anything you wouldn't want on someone else's server, use a local compression method. If it's a resume, a school assignment, or something you wouldn't mind sharing, an online tool is fine and often more effective. Read the privacy policy of any online tool before uploading — some delete files when ready, others keep them longer, and a few may use them for training machine-learning models.

Frequently Asked Questions

Does compressing an image make it look worse?

It depends on the compression level and the original quality. Compressing to "Screen" or "E-mail" resolution (72 to 96 dots per inch) looks fine on a computer or phone but will look blurry if printed. If you might print the document, use "Medium" compression instead. You can always compress again if the file is still too large.

Can I compress a document that's already been compressed?

Yes, but with diminishing returns. If you've already compressed images in Word, compressing the .docx file again with an online tool or zip compression will save only a small amount more. Most of the savings come from the first compression pass.

What's the difference between compressing and converting to PDF?

Compressing shrinks the file size of what you already have. Converting to PDF changes the format — a Word document becomes a PDF. Converting to PDF usually makes the file larger, not smaller, because PDFs embed fonts and flatten images. Compress first, then convert if you need to.

Will compressing a document change what's in it?

Image compression may make pictures slightly less sharp, but the text and content stay the same. Removing pages or deleting formatting changes the content. Compression alone does not.

Is it safe to use free online PDF compressors?

It depends on the tool and what's in your document. Most reputable services (Smallpdf, ILovePDF) delete files after 24 hours and use encryption. But your file does travel to their server, so avoid online tools if the document contains passwords, financial account numbers, or medical information. For sensitive documents, use your computer's built-in compression instead.