Manipulating PDF documents

You can use GNU Ghostscript, gs, to manipulate PDF files. Other tools like qpdf, pdftk, and pdfunite are also available and may be easier to use for some tasks. These can be installed via conda-forge if not already available.

Merge¶

You can merge multiple PDFs using gs:

gs -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf -dBATCH \
    input1.pdf input2.pdf input3.pdf

The backslash (\) allows the command to continue on the next line.

Alternatively, using pdfunite (simpler syntax):

pdfunite input1.pdf input2.pdf input3.pdf output.pdf

Or using qpdf:

qpdf --empty --pages input1.pdf input2.pdf input3.pdf -- output.pdf

Subsetting¶

You can create a new PDF from a subset of the pages in an original PDF using gs, where m and n are the first and last page numbers to extract:

gs -sDEVICE=pdfwrite -dNOPAUSE -dQUIET -dBATCH -dFirstPage=m -dLastPage=n \
    -sOutputFile=output.pdf input.pdf

For example, to extract pages 5-10:

gs -sDEVICE=pdfwrite -dNOPAUSE -dQUIET -dBATCH -dFirstPage=5 -dLastPage=10 \
    -sOutputFile=output.pdf input.pdf

Or using qpdf (e.g., pages 5-10):

qpdf input.pdf --pages . 5-10 -- output.pdf

Compress / Reduce File Size¶

You can reduce the file size of a PDF by reprocessing it with compression settings. The -dPDFSETTINGS option controls the quality/size tradeoff:

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

Quality options (from lowest to highest quality, smallest to largest file):

• /screen - low quality, smallest file (72 dpi)

• /ebook - moderate quality (150 dpi)

• /printer - high quality (300 dpi)

• /prepress - highest quality, largest file (300 dpi, preserves color)

Or using qpdf for compression/optimization:

qpdf --compress-streams=y --recompress-flate input.pdf output.pdf

Convert to Grayscale¶

To convert a color PDF to grayscale:

gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dQUIET \
    -sColorConversionStrategy=Gray -dProcessColorModel=/DeviceGray \
    -sOutputFile=output.pdf input.pdf

Rotate Pages¶

To rotate all pages 90 degrees clockwise (Orientation values: 0=0°, 1=90°, 2=180°, 3=270°):

gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dQUIET \
    -sOutputFile=output.pdf -c "<</Orientation 1>> setpagedevice" \
    -f input.pdf

Convert PDF to PostScript¶

You can convert PDF files to PostScript format using either Poppler’s pdftops or Ghostscript’s pdf2ps:

pdftops input.pdf output.ps

or

pdf2ps input.pdf output.ps

Both commands will create a PostScript file from the PDF input.

Installing Tools¶

Most tools mentioned above are available on SCF Linux systems. If you need to install them locally, you can use conda-forge:

conda install -c conda-forge qpdf poppler