PDF Compression: Reduce PDF File Size for Sharing | FreeFast Blog
Document Conversion
PDF Compression: Reduce PDF File Size for Sharing
FF
FreeFast Team
10 min read
Your PDF is too large. It won't attach to an email. It takes forever to upload. It's eating up your storage. Sound familiar?
PDF compression solves this problem—but done wrong, it turns your crisp document into an unreadable mess. Done right, you can shrink files by 50-90% while keeping everything sharp and readable.
This guide shows you exactly how to compress PDFs properly, whether they're text documents, image-heavy reports, or scanned paperwork.
Why Are PDFs So Large?
Understanding what makes PDFs big helps you compress them smarter.
Adobe's tools offer the most control and best results.
Using Acrobat Pro
Open PDF in Adobe Acrobat Pro
Go to File → Save as Other → Reduced Size PDF
Or for more control: File → Save as Other → Optimized PDF
Choose settings (see optimization section below)
Save the compressed file
Optimized PDF Options
Setting
Effect
Image Settings
Downsample and compress images
Fonts
Unembed fonts, subset fonts
Discard Objects
Remove hidden layers, metadata
User Data
Remove comments, form data
Clean Up
Remove unused elements
"Pro tip: In Acrobat's Optimized PDF dialog, click 'Audit space usage' to see exactly what's making your PDF large. Target the biggest culprits first."
Adobe's Free Online Tool
Don't have Acrobat? Adobe offers free online compression at adobe.com/acrobat/online.
Method 3: Preview on Mac (Built-in)
Mac users have compression built right in.
Step-by-Step Instructions
Open PDF in Preview
Go to File → Export
Click Quartz Filter dropdown
Select Reduce File Size
Save with new name
Important: Mac's default compression is aggressive with images. For documents with important visuals, consider other methods.
Better Quality Option
Create custom Quartz filter via ColorSync Utility
Set image quality to higher values
Apply that custom filter instead
Method 4: Free Desktop Software
For offline work or batch processing.
PDF24 (Windows)
Download PDF24 from pdf24.org
Open and select Compress PDF
Add files and choose quality
Compress and save
LibreOffice (Cross-Platform)
Open PDF in LibreOffice Draw
File → Export as PDF
Reduce quality settings in options
Export
Compression Settings Guide
Different PDFs need different approaches.
For Text-Heavy Documents
Setting
Recommendation
Image compression
Aggressive (text dominates)
Font subsetting
Yes
Resolution
150 DPI (if images present)
Expected compression: 20-40%
For Image-Heavy Documents
Setting
Recommendation
Image compression
Medium (JPEG quality 70-80)
Resolution
150-200 DPI
Color conversion
Keep original
Expected compression: 50-80%
For Scanned Documents
Setting
Recommendation
Image quality
Medium to High
Resolution
200 DPI minimum
Color
Grayscale if possible
Expected compression: 30-60%
"Pro tip: For scanned documents, converting color scans to grayscale often cuts file size in half without losing important information."
How Much Compression to Expect
Realistic expectations based on PDF type:
PDF Type
Typical Compression
Quality Notes
Text only
10-20%
Minimal impact
Text + few images
30-50%
Good results
Many high-res images
60-90%
Depends on settings
Scanned document
40-70%
May affect readability
Already compressed
5-15%
Limited gains
Troubleshooting Common Issues
Problem: Output Is Blurry
Cause: Compression too aggressive for images.
Fix:
Use higher quality setting
Increase minimum DPI (200+)
Choose "Reduce File Size" instead of maximum compression
Problem: File Isn't Much Smaller
Cause: PDF was already well-optimized, or contains mostly text.
Fix:
Check what's actually making the PDF large
Convert images to grayscale
Remove unnecessary pages
Accept that some PDFs can't compress much
Problem: Text Is Harder to Read
Cause: Font embedding changed or image compression affected text scans.
Fix:
Keep fonts embedded
For scanned text: use OCR and higher quality settings
Try different compression tool
Problem: Some Pages Look Worse Than Others
Cause: Inconsistent image quality in source.
Fix:
Compress pages separately
Use uniform quality settings
Re-scan low-quality pages at higher resolution
Best Practices for Smaller PDFs
Before Creating the PDF
Resize images before inserting into documents
Use appropriate resolution (72-150 DPI for screen, 300 for print)
Choose efficient formats (JPEG for photos in docs)
Limit font variety (fewer fonts = smaller file)
When Creating the PDF
Use "Standard" or "Minimum Size" preset when exporting
