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How to Compress a Large PDF File Without Losing Quality

Most large PDFs are big because of high-resolution images or scans. Compressing reduces image resolution and removes unused data. Use PDF24 offline or Adobe’s online tool with a medium setting, or re-export from the original Word document.

Updated
Time
5 minutes
Difficulty
Easy
Applies to
Windows, Mac, Web

By Published Oct 6, 2026

Quick answer

  1. 1 Windows (offline): open PDF24 Creator > Compress PDF, choose a DPI around 150 and quality around 75%, then save.
  2. 2 Any device (online): Adobe Acrobat online Compress PDF > Medium.
  3. 3 Mac: Preview > File > Export > Quartz Filter: Reduce File Size (can lower quality a lot).
  4. 4 From Word: File > Save As > PDF > Minimum size (publishing online).
On this page
  1. Before you start
  2. PDF24 Creator (Windows, offline, free)
  3. Adobe Acrobat online (any device)
  4. Mac: Preview
  5. Re-export from the original document
  6. Troubleshooting
  7. Frequently asked questions

Before you start

  • The large PDF
  • PDF24 Creator or a browser

Method 1 PDF24 Creator (Windows, offline, free)

  1. Step 1: Open the tool

    Install PDF24 Creator and open Compress PDF.

  2. Step 2: Choose settings

    Set DPI to around 150 for on-screen reading (300 for printing) and image quality around 75%.

  3. Step 3: Compress and compare

    Click Compress, check the result, and adjust if text or images look blurry.

Method 2 Adobe Acrobat online (any device)

Avoid online tools for confidential documents.

  1. Step 1: Upload

    Open Adobe’s free Compress PDF tool and select your file.

  2. Step 2: Pick a level

    Choose Medium for a good balance. High compression may blur images.

  3. Step 3: Download

    Download the smaller file.

Method 3 Mac: Preview

  1. Step 1: Export with a filter

    Open the PDF in Preview, choose File > Export, and set Quartz Filter to Reduce File Size.

  2. Step 2: Check quality

    This filter can be aggressive, especially on scans. If images look poor, use another tool.

Method 4 Re-export from the original document

  1. Step 1: Word

    File > Save As (or Export) > PDF and choose Minimum size (publishing online).

  2. Step 2: Compress pictures first

    In Word, select an image > Picture Format > Compress Pictures and choose a lower resolution before exporting.

Troubleshooting

The file barely got smaller

It may be mostly text and fonts, which are already efficient. Try removing unneeded pages or embedded attachments.

Text looks blurry

Use a higher DPI or medium compression; scanned text needs at least 150–200 DPI.

Frequently asked questions

What size limit do email services have?

Usually 20–25 MB. For larger files, share a cloud link instead.

Is “without losing quality” really possible?

Removing unused data and optimising is lossless; reducing image resolution isn’t, but at sensible settings the difference isn’t visible on screen.

Summary

Compress with PDF24 offline or Adobe’s online tool on a medium setting, or re-export from Word with Minimum size. Check the result and use cloud links for files that are still too big.

Sources

Written by

James Chambo

Founder

James is the Founder and Senior Editor of OnlineHow with more than 20 years of experience in internet publishing.