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tamimym
Asked: 2012-03-17 09:12:43 +0800 CST

How can I reduce the file size of a scanned PDF file?

  • 772

I have a 72.9MB PDF file that I need to shrink into under 500KB.

The file was a JPEG image that I had scanned, and then converted to pdf.

pdf compression

24 Answers

  1. Use the following ghostscript command:

    gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook \
-dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

    Summary of -dPDFSETTINGS:

    • -dPDFSETTINGS=/screen lower quality, smaller size. (72 dpi)
    • -dPDFSETTINGS=/ebook for better quality, but slightly larger pdfs. (150 dpi)
    • -dPDFSETTINGS=/prepress output similar to Acrobat Distiller "Prepress Optimized" setting (300 dpi)
    • -dPDFSETTINGS=/printer selects output similar to the Acrobat Distiller "Print Optimized" setting (300 dpi)
    • -dPDFSETTINGS=/default selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file

    Reference: https://www.ghostscript.com/doc/current/VectorDevices.htm#PSPDF_IN:

    Controls and features specific to PostScript and PDF input

    -dPDFSETTINGS=configuration

    Presets the "distiller parameters" to one of four predefined settings:

    • /screen selects low-resolution output similar to the Acrobat Distiller (up to version X) "Screen Optimized" setting.
    • /ebook selects medium-resolution output similar to the Acrobat Distiller (up to version X) "eBook" setting.
    • /printer selects output similar to the Acrobat Distiller "Print Optimized" (up to version X) setting.
    • /prepress selects output similar to Acrobat Distiller "Prepress Optimized" (up to version X) setting.
    • /default selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.

    The exact settings for each of these, including their DPI values, are shown in the dozens of options in this table: https://www.ghostscript.com/doc/current/VectorDevices.htm#distillerparams.

    • 949

  2. My favorite way to do this is to convert the PDF to PostScript and back. It does not always work, though, but when it works the results are nice:

    ps2pdf input.pdf output.pdf

    This also directly works on PDFs, as suggested in the comments.

    Some users also report more success when using the ebook settings as follows:

    ps2pdf -dPDFSETTINGS=/ebook input.pdf output.pdf
    • 262
  3. Best Answer

    aking1012 is right. With more information regarding possible embedded images, hyperlinks etc.. it would be much more easier to answer this question!

    Here are a couple of script and command-line solutions. Use as you see fit.

    • 227

  4. If you have a pdf with scanned images, you can use convert (ImageMagick) to create a pdf with jpeg compression (You can use this method on any pdf, but you'll loose all text informations).

    For example:

    convert -density 200x200 -quality 60 -compress jpeg input.pdf output.pdf

    Adjust the parameters to your needs

    • -density: the pixel density in dpi (e.g. 100x100). Higher pixel densities increase quality and size
    • -quality: the compression ratio. For jpg it is between 1 to 100 with 100 the best quality, but lowest compression
    • -compress: the compression algorithm. jpeg compression might not be the best choice due to compression artifacts. You have the choice between BZip, Fax, Group4, JPEG, JPEG2000, Lossless, LZW, RLE or Zip as alternate compression methods (some only allow b/w images).

    I was able to achieve great compression ratios for scanned/photographed documents (depending on the settings). Depending on the document source, you might want to reduce the color depth (-depth argument).

    • 204

  5. I needed to downsize a PDF that contained full color scans of a document. Each of my pages was a full color image as far as the file was concerned. They were images of pages containing text and images, but they were created by scanning to an image.

    I used a combination of the below ghostscript command and one from another thread.

    gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dDownsampleColorImages=true \
-dColorImageResolution=150 -dNOPAUSE  -dBATCH -sOutputFile=output.pdf input.pdf

    This reduced the image resolution to 150dpi, cutting my file size in half. Looking at the document, there was almost no noticeable loss of image quality. The text is still perfectly readable on my 2012 Nexus7.

    • 66

  6. Here is a script for rewriting scanned pdfs:

    #!/bin/sh

gs  -q -dNOPAUSE -dBATCH -dSAFER \
    -sDEVICE=pdfwrite \
    -dCompatibilityLevel=1.3 \
    -dPDFSETTINGS=/screen \
    -dEmbedAllFonts=true \
    -dSubsetFonts=true \
    -dColorImageDownsampleType=/Bicubic \
    -dColorImageResolution=72 \
    -dGrayImageDownsampleType=/Bicubic \
    -dGrayImageResolution=72 \
    -dMonoImageDownsampleType=/Bicubic \
    -dMonoImageResolution=72 \
    -sOutputFile=out.pdf \
     $1

    You could customise it a bit to make it more reusable but if you only have one pdf, you could just replace $1 with your pdf filename and bung it in a terminal.

    • 40
    1. I use LibreOffice Draw to open the pdf.
    2. I then "export as pdf"
    3. And set "jpeg compression quality" to 50% and "image resolution" to 150 dpi

    This will have a good result.

    • 30

  8. I usually use ps2pdf to do this (easier syntax), something like this:

    ps2pdf -dPDFSETTINGS=/ebook BiggerPdf SmallerPDF

    I use the following python script to reduce the size of all the pdf files in a dir in a production server (8.04). So it should work.

    #!/usr/bin/python

import os

for fich in os.listdir('.'):
        if fich[-3:]=="pdf":
                os.system("ps2pdf -dPDFSETTINGS=/ebook %s reduc/%s" % (fich,fich))
    • 29

  9. Best for me was

    convert -compress Zip -density 150x150 input.pdf output.pdf

    Other ways:

    #### gs
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf $INPUTFILE

### pdf2ps && ps2pdf
pdf2ps input.pdf output.ps && ps2pdf output.ps output.pdf

### Webservice
http://compress.smallpdf.com/de

    regards

    • 19

  10. Referencing this answer and this answer, and after trying a bunch of the answers here, and doing a bunch of research and experimenting, I've come up with the following. Note that I've removed the -dCompatibilityLevel=1.4 part of the command used in some other answers here (including the most-upvoted answer) because this table indicates that 1.5 or 1.7 are automatically used for this setting today (27 Dec. 2020), and there's no need to override those values.

    Use Ghostscript (gs) to compress input.pdf into output.pdf

    3 Main levels of compression:
    Note: you may also add -dQUIET to suppress all output to stdout. See: https://www.ghostscript.com/doc/current/Use.htm.

    1. Low compression: 300 dpi (large file size) 
      gs -sDEVICE=pdfwrite -dPDFSETTINGS=/printer -dNOPAUSE -dBATCH \
-sOutputFile=output.pdf input.pdf
    2. [BEST in my testing] Medium compression (recommended): 150 dpi (medium file size) 
      gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook   -dNOPAUSE -dBATCH \
-sOutputFile=output.pdf input.pdf
    3. High compression: 72 dpi (small file size--may produce grainy or unreadable results in some cases, so try it and give it a shot) 
      gs -sDEVICE=pdfwrite -dPDFSETTINGS=/screen  -dNOPAUSE -dBATCH \
-sOutputFile=output.pdf input.pdf

    You can also add time in front of the command to see how long it takes (this works with any Linux command). Sample output:

    $ time gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=out.pdf in.pdf
GPL Ghostscript 9.50 (2019-10-15)
Copyright (C) 2019 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Processing pages 1 through 15.
Page 1
Loading NimbusSans-Regular font from /usr/share/ghostscript/9.50/Resource/Font/NimbusSans-Regular... 5205104 3852122 2872760 1487237 3 done.
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Page 13
Page 14
Page 15

real    0m1.326s
user    0m1.142s
sys     0m0.048s

    If you add -dQUIET to the command, none of the Ghostscript output is shown, and you get this (when using time in front):

    $ time gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -dQUIET -sOutputFile=out.pdf in.pdf

real    0m1.018s
user    0m0.976s
sys     0m0.040s

    You can also use ps2pdf, which is a wrapper around gs, and produces very similar, but not exactly identical, results. I prefer to just use gs directly, as shown above, however.

    1. Low compression: 300 dpi (large file size) 
      ps2pdf -dPDFSETTINGS=/printer input.pdf output.pdf
    2. Medium compression (recommended): 150 dpi (medium file size) 
      ps2pdf -dPDFSETTINGS=/ebook   input.pdf output.pdf
    3. High compression: 72 dpi (small file size--may produce grainy or unreadable results in some cases, so try it and give it a shot) 
      ps2pdf -dPDFSETTINGS=/screen  input.pdf output.pdf

    PDF Compression Tests

    Testing the gs commands above on output from my pdf2searchablepdf script here, I see the following:

    1. Low compression: has no significant effect since my script already produces 300 dpi output PDFs. So, a 3.8 MB 3 pg input PDF results in an output PDF of ~3.8MB.
    2. [BEST] Medium compression: compresses the file nicely! A 3.8 MB 3 pg input PDF results in an output PDF of ~0.95MB.
    3. High compression: may be too much. A 3.8 MB 3 pg input PDF results in an output PDF of ~0.37MB, BUT in my particular test is completely unreadable, since the input PDF was already of somewhat poor resolution to begin with. If you begin with a high quality/high resolution input PDF, you may have much better, readable results.

    Ghostscript (gs) Documentation:

    For all -d ("define") PDFSETTINGS available, see here: https://www.ghostscript.com/doc/current/VectorDevices.htm#PSPDF_IN. I have quoted that section below, except that I've added the DPI values for each setting in bold, as taken from this table here. You can refer to that table to see the dozens of lower-level settings chosen by gs for each PDFSETTINGS option.

    Controls and features specific to PostScript and PDF input

    -dPDFSETTINGS=configuration

    Presets the "distiller parameters" to one of four predefined settings:

    • /screen (72 dpi) selects low-resolution output similar to the Acrobat Distiller (up to version X) "Screen Optimized" setting.
    • /ebook (150 dpi) selects medium-resolution output similar to the Acrobat Distiller (up to version X) "eBook" setting.
    • /printer (300 dpi) selects output similar to the Acrobat Distiller "Print Optimized" (up to version X) setting.
    • /prepress (300 dpi) selects output similar to Acrobat Distiller "Prepress Optimized" (up to version X) setting.
    • /default (72 dpi) selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.

    You can also see definitions for various options on this page: https://www.ghostscript.com/doc/current/Use.htm:

    -dNOPAUSE
    Disables the prompt and pause at the end of each page. Normally one should use this (along with -dBATCH) when producing output on a printer or to a file; it also may be desirable for applications where another program is "driving" Ghostscript.

    -dBATCH
    Causes Ghostscript to exit after processing all files named on the command line, rather than going into an interactive loop reading PostScript commands. Equivalent to putting -c quit at the end of the command line.

    -dQUIET
    Suppresses routine information comments on standard output. This is currently necessary when redirecting device output to standard output.

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