# How to Reduce PDF File Size Without Losing Noticeable Quality
PDFs can grow very large, especially those containing high-resolution images or fully embedded fonts. This guide covers the most effective techniques for reducing size without noticeably impacting quality.
## Why is your PDF large?
Before compressing, understand what's making it big:
| Cause | Typical size impact |
|-------|---------------------|
| High-resolution images | 80–95% of the file size |
| Fully embedded fonts (not subsetted) | 5–20 MB per font |
| Unnecessary layers, comments, bookmarks | 1–5 MB |
| Embedded videos or file attachments | Variable |
| Previous versions without "Save As" | Can double the file size |
## Option 1: Online tool
1. Go to [KaijuConverter — compress PDF](/convert/pdf-to-pdf) or ilovepdf.com
2. Upload the PDF
3. Choose compression level
4. Download the result
Ideal for occasional PDFs. Typical compression: 30–70%.
## Option 2: Ghostscript (free, command line)
**Ghostscript** is the reference engine for PDF manipulation — it's what most online "PDF compressors" use internally.
```bash
# Install
sudo apt install ghostscript # Ubuntu/Debian
brew install ghostscript # macOS
# Windows: download installer from ghostscript.com
# Compress for web (72 DPI, low image quality)
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/screen \
-dNOPAUSE -dQUIET -dBATCH \
-sOutputFile=compressed.pdf original.pdf
# Compress for email/ebook (150 DPI, medium quality)
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/ebook \
-dNOPAUSE -dQUIET -dBATCH \
-sOutputFile=compressed.pdf original.pdf
# Compress for printing (300 DPI, high quality)
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/printer \
-dNOPAUSE -dQUIET -dBATCH \
-sOutputFile=compressed.pdf original.pdf
```
**dPDFSETTINGS levels:**
- `/screen`: 72 DPI — smallest size, lowest image quality
- `/ebook`: 150 DPI — good balance for digital distribution
- `/printer`: 300 DPI — quality for standard printing
- `/prepress`: 300+ DPI — professional printing (no quality reduction)
## Option 3: Adobe Acrobat Pro
If you have Acrobat Pro, use **Save as Optimized PDF**:
1. File → Save As Other → Optimized PDF
2. **Images** panel: reduce resolution (150 DPI for screen, 300 for print)
3. **Fonts** panel: enable "Unembed all fonts" if the recipient doesn't need to edit
4. **Discard Objects** panel: remove comments, bookmarks, unused forms
5. **Clean Up** panel: remove data from previous versions
This option gives you the greatest control over what gets compressed.
## Option 4: Reduce images BEFORE creating the PDF
The most effective compression happens at the source:
1. In Word/LibreOffice: before exporting to PDF, compress the document's images
- Word: click image → Format Picture → Compress Pictures → for web use
2. In Photoshop: save images at 72–150 DPI before inserting into the document
## Expected compression by PDF type
| PDF type | Typical reduction |
|----------|------------------|
| Report with high-resolution photos | 50–85% |
| PowerPoint presentation | 40–70% |
| Text document with few images | 5–20% |
| Scanned PDF at 600 DPI | 60–80% |
| Vector PDF (diagrams, logos) | 10–30% |
## Batch compress multiple PDFs
```bash
#!/bin/bash
# Compress all PDFs in the current folder to /ebook level
for f in *.pdf; do
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
-dPDFSETTINGS=/ebook \
-dNOPAUSE -dQUIET -dBATCH \
-sOutputFile="${f%.pdf}_compressed.pdf" "$f"
echo "Compressed: $f"
done
```
With the right techniques, most PDFs can be reduced by 40–80% with no noticeable quality difference for the end user.
Guide