DiffPDF

DiffPDF is a tiny and portable piece of software that allows you to compare two PDF files when it comes to the words, characters and appearance. It can be seamlessly handled, even by users with less or no experience in such apps.
As installation is not a prerequisite, you can just drop the program files on any location of the hard drive and run the executable file directly.
But you may also save DiffPDF to a USB flash drive or similar external device, and run it on any computer. Plus, you can carry the app with you whenever you're on the move.
Concerning the operating system, no items are left behind in the Windows Registry (reducing the risk of system crashes) or on the hard drive after removing the application.
The app is wrapped in a standard interface with a plain layout. DiffPDF clearly does not excel in the visual department, but it's simple to navigate. Opening two PDF files is done by using either the file browser or "drag and drop" functionality.
Differences between the two PDF items can be noticed by viewing their content, since they are highlighted in red, according to the comparison type of your choosing. In addition, you can zoom in and out, exclude margins from the comparison, view log details, as well as set up separate zones in the layout (e.g. number of columns, tolerance).
A few other settings can be configured from the Options screen. For example, you can hide the tooltips in the main application window, change the default base color, outline and fill color for the highlighting, as well as specify the square and cache sizes.
The straightforward software tool uses a moderate amount of CPU and system memory, has a good response time and displays instant results. No error dialogs have been shown in our tests and the program did not hang or crash; we haven't encountered any issues. Thanks to its intuitive layout and overall simplicity, DiffPDF should be able to please the entire audience.