How would I go about this?

I have a ton of grouped pdf files that I need to store in such a way that I can read and search them in the fastest way possible. Write/Annotate/Delete times are not important.

* The pdfs are already grouped by various themes and alphanumerically. This should facilitate searching.

* Average file size is about 2MB.

* There are about 2.5M files

How would I go about this?

>>1
I have never seen a pornographic pdf, much less a collection of those.