PDFResurrect is a tool aimed at analyzing PDF documents. The PDF
format allows for previous document changes to be retained in a more
recent version of the document, thereby creating a running history of
changes for the document.  This tool attempts to extract all previous
versions while also producing a summary of changes between versions.
This tool can also "scrub" or write data over the original instances
of PDF objects that have been modified or deleted, in an effort to
disguise information from previous versions that might not be intended
for anyone else to read.