How to shrink/split large PDF to less than 50 MB

Question

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.

Answer 1

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.

Answer 2

PDF Scissors was developed to take the hassle out of PDF reading on Kindles. It may be beneficial to you.

http://www.pdfscissors.com/

Answer 3

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.