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How to Compress a PDF File for Free (Reduce PDF Size)

4 min read •
Beginner PDF Compress File Size Free Tool

Your PDF is 25 MB but the upload limit is 10 MB. Or you need to email a document but it is too large to attach. This is one of the most common everyday problems — and it has simple solutions.

This guide shows you how to reduce PDF file size using free methods, plus how to prevent oversized PDFs in the first place.

Why Are PDFs So Large?

The biggest culprits:

Cause Typical Size Impact
High-resolution images A single 4000×3000 photo can be 5-10 MB
Scanned documents at 600 DPI 2-5 MB per page
Embedded fonts 0.5-2 MB per font family
Uncompressed images PNG images inside PDF are much larger than JPG
Multiple pages Each page with images adds up fast

A 10-page document with photos can easily reach 50-100 MB.

Method 1: Reduce Image Size Before Creating the PDF

The most effective approach — shrink the images before they go into the PDF.

Resize Images First

Use our Image Resizer:

  • Resize photos to 1200-1500 pixels wide (plenty for on-screen reading)
  • Use 80% quality for JPG — visually identical but 3-5x smaller
  • Do not use 4000×3000 photos in a document meant for screens

Use JPG Instead of PNG

Format 1200×800 photo
PNG ~3 MB
JPG (90% quality) ~300 KB
JPG (80% quality) ~150 KB

That is a 20x size difference. Use our PNG to JPG converter before creating the PDF.

Lower Scan Resolution

If scanning documents:

  • 200 DPI — good enough for readable text
  • 300 DPI — standard quality, good for printing
  • 600 DPI — overkill for most purposes, creates huge files

Going from 600 DPI to 200 DPI reduces file size by about 9x.

Method 2: Rebuild the PDF with Smaller Images

If you already have a large PDF made from images:

  1. Extract the pages/images
  2. Resize them with our Image Resizer
  3. Recombine them with our Image to PDF tool

This gives you full control over the output quality and size.

Method 3: Print to PDF (Quick Fix)

Every operating system has a "Print to PDF" feature that recompresses the content:

Windows

  1. Open the PDF in any viewer
  2. Ctrl+P (Print)
  3. Select "Microsoft Print to PDF"
  4. Print → save with a new name

This often reduces size by 30-50% because it recompresses images.

Mac

  1. Open the PDF in Preview
  2. File → Export
  3. In the "Quartz Filter" dropdown, select "Reduce File Size"
  4. Save

Linux

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH \
   -sOutputFile=compressed.pdf original.pdf

Quality presets:

  • /screen — lowest quality, smallest file (72 DPI)
  • /ebook — medium quality (150 DPI) — best balance
  • /printer — high quality (300 DPI)
  • /prepress — highest quality, largest file

Method 4: Remove Unnecessary Content

Before compressing, check if you can simply remove things:

  • Delete blank pages — use our PDF Split & Merge to extract only the pages you need
  • Remove cover pages or appendices if not needed
  • Split the PDF — if only part is needed for the upload, extract those pages

Size Targets for Common Uses

Purpose Target Size How to Achieve
Email attachment Under 10 MB (Gmail: 25 MB) Resize images to 1200px, use JPG
Online form upload Check the limit (often 5-10 MB) Aggressive compression
Cloud storage No hard limit Moderate compression
Printing Quality matters more than size Use 300 DPI, minimal compression
Archival Keep original quality Do not compress

Quick Size Reduction Checklist

  1. Are there images? → Resize them to 1200px wide max
  2. Are images PNG? → Convert to JPG with our PNG to JPG
  3. Are there unnecessary pages? → Remove them with PDF Split & Merge
  4. Still too large? → Print to PDF for recompression
  5. Was it scanned at 600 DPI? → Rescan at 200-300 DPI

Frequently Asked Questions

Will compression make text blurry? No. Text in PDFs is usually vector-based and stays sharp regardless of compression. Only embedded images lose quality.

How small can I make a PDF? A text-only PDF is typically 50-200 KB per page. A PDF with images depends entirely on the images — anywhere from 100 KB to 10 MB per page.

Why did my PDF get larger after compression? This can happen if the "compression" tool re-encodes already-compressed images. The Print-to-PDF method sometimes increases size if the original was already well-optimized.

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