Since the user is using an online ordering system, I expect that the info is saved to a database.
You will have three options to get the data from the database.
1) Create a DSN and link the form directly to the OLEDB database using the DSN.
2) Bind a schema to the form and generate the data from the DB in the form of XML and then render the PDF with the XML data. You ned to have workbench server software for this.
3) Develop a webservice to retrieve the data and in your form, create a dataconnection using the webservice to get the data.
For the options 1) and 3) above, you need to have the reader extensions server software to communicate with the database/ webservice.
Hope this give some ideas to you..
Thanks
Srini