Working with pdf files
Install qpdf:
sudo apt install qpdf
See docs on qpdf: https://qpdf.readthedocs.io/en/stable/cli.html
To rotate a pdf file 180 degrees:
qpdf in.pdf out.pdf --rotate=+180
or, if you’re ok with modifying your original pdf file:
qpdf in.pdf --replace-input --rotate=+180
To join a bunch of pdf files into one file:
pdfunite in-1.pdf in-2.pdf in-3.pdf out.pdf
For more precise control, use qpdf.