We currently don't offer volume purchasing for ExportPDF. We do offer this for CreatePDF. You can read more about this here:
CPDF Team Features: https://www.acrobat.com/createpdf/en/team-plan.html
CPDF Team Pricing: https://www.acrobat.com/createpdf/en/pricing/team-pricing.html
I added this idea of ExportPDF volume purchasing to our Ideas site: http://forums.adobe.com/ideas/1548
Please go and make a comment and vote on this idea, if you'd like to see us impliment this in the future.