Differ tools, which compare two files and visually highlight the differences between them, exist for many file and archive formats. These programs are particularly useful if you have two or more versions of a file and cannot see the differences immediately. Many of these comparison tools are command-line-based and require knowledge of an extensive set of parameters. If you need to compare PDF files, DiffPDF [1], with its graphical user interface, compares both the text components of two PDF files as well as the embedded images for differences.

According to the original developer, the free version of DiffPDF is no longer under active maintenance due to the European Union's 2024 Cyber Resilience Act [2]. As a result, the binary package is no longer available on the DiffPDF website. Instead, you need to download it from your distribution's repository. You will find DiffPDF in the repositories of most of the popular distributions [3] and can conveniently install it with your distribution's package manager. Doing so creates a starter in the main menu. You can also run the software at a prompt. For an overview of parameters, use the diffpdf --help command. The graphical version also comes with a help function that explains the tool's individual functions.

On first launch, a three-pane program window pops up. When loaded, the files to be compared appear in the two larger panes on the left and in the middle. Above this, there is a single line with the fields for the file names and paths. You can see the actual controls in the third window segment on the far right. The Controls tab and the matching dialog are shown at the top. The Actions dialog is located in another tab line at the bottom. However, you will not find a menubar or a buttonbar.

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