DIFF program capable of comparing a large number of texts

Hi
We are currently writing our master thesis, and are in great need of a specific program. We have no idea whether or not it actually exists, but what we are looking for is a program capable of comparing about 500 texts simultaneously in order to find differences/similarities between the texts – and being able to report about these cross-references. A dreamscenario would be if it’s also capable of giving a procentage of the differences in between the texts.
We are aware that some of the different diff-programs are able to compare two texts – but we really need it to be able to comprehend more than that.

What we want to do is to compare annual reports to find out whether or not companies "borrow" text from each other, when writing the annual report.
Therefore, we need the program to take 1 text at a time and compare it to the others (prox. 500) to find overlapping between them.
Quite like when universities compare exam thesis with old exam thesis, to se whether or not there has been "copy/paste"

It´s preferable if the program can be installed on a windows computer, furthermore if it is possible for the program to load *.pdf files


Hope that you – or someone else – are able to help us.

What you are looking for is an kind of a very advance Text Analyzer. In this you need facilities copy paste checker, percentage of repeated and similar text, etc. There are some online tools that are capable of analyzing a text on a document. Second you a need to find difference between documents and overlapping the same. There is a tool called ExamDiff. This tool lets you to compare two documents with each other and highlights the similarities. And if you are looking for more customization then you might need any developer who create a program like this for you.