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

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---
title: Make PDF files smaller
excerpt: 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)
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## 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 "$1")
gs \
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-sOutputFile="$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**:
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- */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.
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## PDFs in a folder
Use the following script to compress all PDFs in a folder.
Usage: `sh pdfcompress.sh 'target folder'`
*If `'target folder'` is not specified, defaults to current directory.*
```bash
#!/bin/sh
if [ -n "$1" ]; then
cd "$1"
fi
for i in *.pdf; do
[ -f "$i" ] || break
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# Skip compressed PDFs
echo "$i" | grep --quiet ".compressed.pdf"
if [ $? = 1 ]; then
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gs \
-sOutputFile="${i%.*}.compressed.pdf" \
-sDEVICE=pdfwrite \
-dPDFSETTINGS=/ebook \
-sColorConversionStrategy=Gray \
-sColorConversionStrategyForImages=/Gray \
-dProcessColorModel=/DeviceGray \
-dCompatibilityLevel=1.4 \
-dNOPAUSE -dBATCH -dQUIET \
"$i"
fi
done
```
If you prefer to use the original filename as the compressed version and rename the original uncompressed's to "*.original.pdf",
*Following script doesn't skip previously compressed PDFs*
```bash
#!/bin/sh
if [ -n "$1" ]; then
cd "$1"
fi
for i in *.pdf; do
[ -f "$i" ] || break
# Rename original file to *.original.pdf
original="${i%.*}.original.pdf"
mv "$i" "$original"
gs \
-sOutputFile="$i" \
-sDEVICE=pdfwrite \
-dPDFSETTINGS=/ebook \
-sColorConversionStrategy=Gray \
-sColorConversionStrategyForImages=/Gray \
-dProcessColorModel=/DeviceGray \
-dCompatibilityLevel=1.4 \
-dNOPAUSE -dBATCH -dQUIET \
"$original"
done
```
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<br/><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)