There is one way to do this that I know of. First, you need a Mac that has been AirPrint enabled by using the Hacktivator or similar method. Then download and install the CUPS-PDF package and install and share the printer. Choose this printer when printing from an iPad. PDFs are then spooled to /Users/shared/CUPS-PDF/ANONYMOUSNo you can not print to a PDF on the iPad.