Hi Chris:

Assuming your files are available in a directory like:

why not use the manifest file:

It will help you determine what files need to be downloaded, and the
expected md5 checksum for the file once downloaded. This will at least
guarantee that you've got the files you need and that they've made it
over the wire ok. If you are really wanting to be thorough you could
run the PDFs through something like JHOVE to make sure they look legit
I guess.