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I have a large tech PDF. It's 2500 pages with images and 100 MB in size. I'd like to try and read it on my Kindle. To my understanding, PDFs have to be less than 50 MB in order to read on the Kindle.

I downloaded PDFSAM, but if it splits the PDF into multiple PDFs by the number of pages, the file size doesn't seem to shrink more than 5 MB (so 95MB). I even tried breaking the PDF down every 100 pages.

It has a feature that will split by file size, but it doesn't seem to do anything to this PDF.

Is there a free way that I can get it down to less than 50 MB? I don't know if I can lower the quality of the PDF to make it smaller (might not be drastic enough though), split it up into multiple ones less than 50 MB, or even strip the images out of it.

I tried Calibre, which converted the file to a MOBI format. However, the MOBI file was about 200MB, and Gmail wouldn't accept it as an email attachment.

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afaik, a mobi file is a zip file. try renaming the mobi to "zip" and then extract it. you will be able to identify the reason for the large file sizes. Presumably the images are the problem. –  horatio Dec 27 '12 at 18:26
1  
Have you tried printing to a i.e. PDF Creator but just pages 1-100 and checking what the output file size is? –  Darius Dec 27 '12 at 18:30
    
What operating system are you using? –  l1zard Dec 27 '12 at 19:44
    
@l1zard Windows8 and/or OSX Lion –  Hoppe Dec 27 '12 at 21:14
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You are right, there's something really weird about this file. I don't know if it's corrupted or what. I used pdftk's burst mode to split it into individual pages, and even though most pages contained text they each were around ~90MB! Just doesn't make sense. :/ –  Karan Dec 28 '12 at 16:10
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3 Answers

up vote 2 down vote accepted

You could delete all images from a copy of the PDF, via a few lines of either: Java, C#, or VB.Net, alternatively you could use the PDF->Mobi conversion tool in Calibre, as this can reduce image quality to suit a kindle.

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The Aspose library is $800 for a single license. Calibre didn't reduce the file size when it converted it to Mobi... It made it bigger. –  Hoppe Dec 27 '12 at 21:22
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What options did you set for the Calibre conversion e.g. ebook-convert --no-images someFile.pdf someFile.mobi Also note: Aspose offers a 30 day trial, while the pdfbox libraries and Calibre App are FREE. –  arober11 Dec 29 '12 at 14:25
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PDF Scissors was developed to take the hassle out of PDF reading on Kindles. It may be beneficial to you.

http://www.pdfscissors.com/

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I just tried PDF scissors. It was helpful to remove the margins, but for some reason the PDF actually got 5 MB bigger :( –  Hoppe Dec 27 '12 at 18:21
    
@Hoppe Thx for the feedback, the only other good tool I know is sejda.com –  Simon Dec 27 '12 at 20:43
    
thank you for the suggestions. Ironically the limit on Sedja.com is 50 MB as well –  Hoppe Dec 27 '12 at 21:46
    
@Hoppe I hope something turns up, if I find out more I will let you know –  Simon Dec 27 '12 at 23:07
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You can try the instructions of this page (Linux only) (french): Optimiser un fichier PDF sous Linux.

Install needed software:

sudo apt-get install poppler-utils ghostscript

Provice original PDF file path:

PDF_FILE="original.pdf"

Provide output PDF file path:

OPTIMIZED_PDF_FILE="optimized.pdf"

And run the optimization:

command pdftops \
        -paper match \
        -nocrop \
        -noshrink \
        -nocenter \
        -level3 \
        -q \
      "$PDF_FILE" - \
  | command ps2pdf14 \
        -dEmbedAllFonts=true \
        -dUseFlateCompression=true \
        -dProcessColorModel=/DeviceCMYK \
        -dConvertCMYKImagesToRGB=false \
        -dOptimize=true \
        -dPDFSETTINGS=/prepress \
      - "$OPTIMIZED_PDF_FILE"

Alternatively, you can use this command line to reduce the image quality to 72dpi:

command pdftops \
        -paper match \
        -nocrop \
        -noshrink \
        -nocenter \
        -level3 \
        -q \
      "$PDF_FILE" - \
  | command ps2pdf14 \
        -dEmbedAllFonts=true \
        -dUseFlateCompression=true \
        -dOptimize=true \
        -dProcessColorModel=/DeviceRGB \
        -dUseCIEColor=true \
        -r72 \
        -dDownsampleGrayImages=true \
        -dGrayImageResolution=72 \
        -dAutoFilterGrayImages=false \
        -dGrayImageDownsampleType=/Bicubic \
        -dDownsampleMonoImages=true \
        -dMonoImageResolution=72 \
        -dMonoImageDownsampleType=/Bicubic \
        -dDownsampleColorImages=true \
        -dColorImageResolution=72 \
        -dAutoFilterColorImages=false \
        -dColorImageDownsampleType=/Bicubic \
        -dPDFSETTINGS=/prepress \
      - "$OPTIMIZED_PDF_FILE"

These commands are implemented online by PdfCruncher.

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