I have Adobe Acrobat Professional 8.0 on a PC I use at school. I am able to print documents to Adobe PDF and create them into a PDF by choosing Adobe PDF instead of a printer.
I have purchased an eBook that opens in Adobe Digital Editions. The book allows unlimited printing.
Is it possible to print parts of the book to PDF and create a PDF instead of printing the pages out onto paper?
No, this is expressly disallowed. If you think about it, that would allow you to circumvent the DRM protection and the publishers therefore forbid this.