What is the best way to handle PDF to JPG page number conversions

[guyfromfl]

I have a script that takes a 2 or 3 page pdf, uploads it and hashes the file name to something that isn't guessable. 

 

We now want to add an image of each of the PDF for users who don't have Adobe Reader.  Some pdf's will be 2 and some 3 pages.

 

Should I:

A) Let convert name the different pages "*-0.jpg, *-1.jpg..." and then use a recursion function (it's already written for another reason) to crawl the folder,

B) Use a PHP/PDF library to determine the number of pages, then add the value to the database's corresponding row.

C) Use a hybrid of both

D) Any better ideas???

 

Thanks