Further on the topic of the previous post but more on to manual compare. DWF Version Compare was introduced in Autodesk Design Review 2008. You find it on the Tools menu. This can be useful when comparing two DWF files. But be aware that it has its limitations like it cannot find differences on raster objects and the DWF files must be the same sheet size and use the same units.
If you want to compare PDF files Adobe Acrobat Professional have that functionality and works great with large multipage documents. Found on the Advanced menu. It’s a real time saver when you get PDF files like specifications from a customer, client or colleague and don’t want to read through everything a second time just to find the changes. Below you can see some of the result from Acrobat compare.
Microsoft Word also have this functionality to compare two versions of a document. I have found not many are aware of it. In Word 2007 it is on the Review tab.