Install libqpdf21 by entering the following commands in the terminal:
sudo apt update sudo apt install libqpdf21
runtime library for PDF transformation/inspection software
QPDF is a program that can be used to linearize (web-optimize), encrypt (password-protect), decrypt, and inspect PDF files from the command-line. It does these and other structural, content-preserving transformations on PDF files, reading a PDF file as input and creating a new one as output. It also provides many useful capabilities to developers of PDF-producing software or for people who just want to look at the innards of a PDF file to learn more about how they work. . QPDF understands PDF files that use compressed object streams (supported by newer PDF applications) and can convert such files into those that can be read with older viewers. It can also be used for checking PDF files for structural errors, inspecting stream contents, or extracting objects from PDF files. QPDF is not PDF content creation or viewing software -- it does not have the capability to create PDF files from scratch or to display PDF files. . This package contains the qpdf runtime libraries required to run programs that link with the qpdf library.