There are probably 100 ways to do that. I've seen at least 20 myself.
But before you go down that road, you really need to examine the work flow here. To prevent errors (and to skip headaches like the one you're having now), the correct way to build this system is to have the original ordering system output the order twice.
It can still output a PDF for the users... but then at the same time, it should be writing the details of the order to a database or, at the very least, an XML or a CSV file.
I'm talking about good programming. Good system design. It's better for the client and it's better for you. Someday, someone is going to ask that the PDF's get formatted differently and you will have to modify your PDF data extraction script again - if it can even be done. (Imagine if they said, we want the order total displayed in graphics, not text. Now your import script can't work no matter what).
The system you are designing is called a kludge - and I understand the appeal, it's the fastest way to be done. But trust me, after 30 years of programming, the simplest solution is always best. Tell the client that they can pay $300 more today to do it right... or $8000 more in five years from now to clean up the mess.