Adobe Acrobat Professional offers features letting users compare PDF Documents showing the differences between two versions of a file, however the software suite is not free - but fortunately we have free utilities to get the task done easily.

Free, open-source, cross-platform and portable utility DiffPDF allows users to compare PDF files visually for changes supporting two comparison-modes - Text and Appearance, the text comparison mode highlights text-changes while the appearance mode also takes care of any changes made to embedded images.