Manish6,
Do you want to compare multiple versions of your website’s report taken at different timing (morning, lunch time, afternoon tea time, evening) and find differences between these versions?
Then I think you will find a big technical challenge. That is, you would need to store these versions in a folder tree like this:
<base>/<TestSuite Id>/<TestSuite Timestamp>/<TestCase Id>/<subpath>/<filename.pdf>
Your step2 script would store downloaded files into this folder tree. The tree format keeps downloaded files manageable/identifiable for the step3 script. You would need a set of access methods to the files in the tree.
I have ever been struggling with this problem (for screenshot images) in the last 9 months, and got a favorable solution for it. See the following post: