How can I extract a page range / a part of a PDF?

pdftk is a useful multi-platform tool for the job (pdftk homepage).

pdftk full-pdf.pdf cat 12-15 output outfile_p12-15.pdf

you pass the filename of the main pdf, then you tell it to only include certain pages (12-15 in this example) and output it to a new file.

Installation instructions:

To install the snap version, which is an unofficial repackaging of an old version of PDFtk (repackaged by Scott Moser), visit this link or run:

sudo snap install pdftk

Alternatively, you can install an open source port of PDFtk to Java by Marc Vinyals, by running:

sudo apt install pdftk-java

Another alternative is PDFtk Server, available from the website: https://www.pdflabs.com/tools/pdftk-server/ . This version is free of charge for personal use, but it is not open source.

Very simple. Use the default PDF reader, select "Print To File" and that's it!

Then:

Note that with this way, the text will no more be searchable, instead all texts are converted to images: this is how "Print" works.