Working with PDF files

Required tools: gs (ghostscript), qpdf, pdfseparate, pdftoppm.

• Reduce the size of a scanned PDF, the value for "quality" option can be:
  screen,ebook,printer,prepress

  gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/{quality} -dNOPAUSE -dQUIET -dBATCH -sOutputFile={output.pdf} {input.pdf}
  

• Merge multiple PDF files:

  gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE={output.pdf} -dBATCH {input1.pdf} {input2.pdf}
  

• Remove password:

  gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sPDFPassword={password} -f -sOutputFile={output.pdf} {input.pdf}
  
  qpdf --password={password} --decrypt {input.pdf} {output.pdf}
  

• Extract pages from a PDF file:

  pdfseparate -f {first page} -l {last page} {input.pdf} {output.pdf}
  

• Convert a PDF file to images; define horizontal and vertical DPI to generate the images, 150 is the default value if dpi not specified.

  pdftoppm -png -rx {horizontal dpi} -ry {vertical dpi} {input.pdf} {output prefix}
  
  # If document.pdf has two pages
  
  pdftoppm -png document.pdf img
  
  # Will produce img-1.png, img-2.png
  

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