qpdf

Command-line tools and library for transforming PDF files

QPDF is a program that does structural, content-preserving transformations on PDF files. It could have been called something like pdf-to-pdf. 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 offers many capabilities such as linearization (web optimization), encrypt, and decryption of PDF files. Note that QPDF does not have the capability to create PDF files from scratch; it is only used to create PDF files with special characteristics starting from other PDF files or to inspect or extract information from existing PDF files.