diff-pdf is a tool for visually comparing two PDFs. It takes two PDF files as arguments. By default, its only output is its return code, which is 0 if there are no differences and 1 if the two PDFs differ. If given the --output-diff option, diff-pdf produces a PDF file with visually highlighted differences: $ diff-pdf --output-diff=diff.pdf a.pdf b.pdf Another option is to compare the two files vi