DiffPDF enables you to compare the content of two PDF files side by side. The program offers a textual comparison mode as well as a visual comparison. The text comparison mode looks for differences in the text content of the file and highlights any differences that it finds. The visual comparison mode on the other hand looks for differences in the appearance like paragraphs, images and even differences in diagrams.
You have the option to save the comparison results as a PDF file that shows the pages that differ with their differences highlighted.