I tried adding this to count the number of 'Type/Page' appearing in the document, and that worked until I tried with you document :
That returned 28 pages instead of 16. So I just had a look at
Count The Number of Pages in a PDF - PHP - Snipplr (thanks wirehopper ) and the first message gave me the solution (using Ubuntu Karmic) :
It worked perfectly on your document. I will keep this one. Simple, fast and efficient.