Unfortunately pre-generating the PDF is not an option. The whole system is essentially a web2print solution, users login to the system, build how they want the pdf to look using an html/js interface, and then when they are happy with how it looks, they hit 'build'. At the moment with only a few users it is relativly uncommon for more than 2 requests to happen at any one time, however due to new clients I am having to make the system ready for a much larger scale. Depending on how much the system needs to be scaled I am thinking of a system whereby when a user wants to build a pdf, it puts an entry into a database, this will be their 'ticket'. I will then run the script as a daemon, which will check for an entry in the database, process it, create the pdf, then remove the entry, and wait until another 'ticket' is collected.