blog/source/_posts/make-pdf-files-smaller.md

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---
title: Make PDF files smaller
subtitle: Convert to grayscale and reduce the resolution.
date: 2019-01-05
tags:
- PDF
---
The most effective ways of reducing the file size of a PDF is by converting to grayscale and reduce the resolution.
Requirement: ghostscript (installed by default in Ubuntu)
## Single PDF
Save the following script as "pdfcompress.sh".
Usage: `sh pdfcompress.sh input.pdf`
The output compressed file is named as "input.compressed.pdf"
```bash
#!/bin/sh
filename=$(basename "$1")
dir=$(dirname "$1")
gs \
-sOutputFile="$dir/${filename%.*}.compressed.pdf" \
-sDEVICE=pdfwrite \
-dPDFSETTINGS=/ebook \
-sColorConversionStrategy=Gray \
-sColorConversionStrategyForImages=/Gray \
-dProcessColorModel=/DeviceGray \
-dCompatibilityLevel=1.4 \
-dNOPAUSE -dBATCH -dQUIET \
"$1"
```
Options ([more info](https://ghostscript.com/doc/current/Ps2pdf.htm#Options)):
- Remove **ColorConversionStrategy**, **ColorConversionStrategyForImages** and **ProcessColorModel** lines to retain colour.
- **PDFSETTINGS**:
- */default* selects output intended to be useful across a wide variety of uses. 72 DPI.
- */screen* selects low-resolution output similar to the Acrobat Distiller "Screen Optimized" setting. 72 DPI.
- */ebook* selects medium-resolution output similar to the Acrobat Distiller "eBook" setting. 150 DPI.
- */printer* selects output similar to the Acrobat Distiller "Print Optimized" setting. 300 DPI.
- */prepress* selects output similar to Acrobat Distiller "Prepress Optimized" setting. 300 DPI.
## PDFs in a folder
Use the following script to compress all PDFs in a folder.
Usage: `sh pdfcompress.sh 'target folder'`
```bash
#!/bin/sh
cd "$1"
for i in *.pdf; do
[ -f "$i" ] || break
# Skip compressed PDFs
echo "$i" | grep --quiet ".compressed.pdf"
if [ $? = 1 ]
then
gs \
-sOutputFile="${i%.*}.compressed.pdf" \
-sDEVICE=pdfwrite \
-dPDFSETTINGS=/ebook \
-sColorConversionStrategy=Gray \
-sColorConversionStrategyForImages=/Gray \
-dProcessColorModel=/DeviceGray \
-dCompatibilityLevel=1.4 \
-dNOPAUSE -dBATCH -dQUIET \
"$i"
fi
done
```
<br/>
Source: [Internal Pointers](https://www.internalpointers.com/post/compress-pdf-file-ghostscript-linux), [firstdoit](https://gist.github.com/firstdoit/6390547), [ahmed-musallam](https://gist.github.com/ahmed-musallam/27de7d7c5ac68ecbd1ed65b6b48416f9), [Ghostscript Docs](https://ghostscript.com/doc/current/Ps2pdf.htm)