I found the Adobe Interapplication Communication API Reference document that seems to be right for you. The methods offered by the LabVIEW invoke node (those associated with the AxAcroPDF object) are described starting from page 106, but if you find a way to implement the GetPageNum method of the AVPageView object (page 50) you are OK. Unfortunately, I don't have time currently to look into this in more detail, but I hope this helps you move forward.
UPDATE: According to this thread, I'm afraid that what you want to do can't be done. 😞