goodroi - 1:51 pm on Nov 24, 2011 (gmt 0)
I can think of many ways to monetize PDFs. You can add affiliate links to your PDF. In the content of the PDF you can talk about and promote your company's products/services/ebooks/whatever. Link juice flows through PDFs so you can sell links. You can also sell ad placement or banner placement.
You need to be careful to keep a balance between monetizing and providing value. For example if you replace your informative content with 100% promotional copy users will not be interested and this will lead to poor user engagement plus people are alot less likely to link to promotional copy.