page = doc:InsertPage(target)
doc:InsertPage() creates a new page and inserts it just before the specified page.
doc:InsertPage() returns the handle of the newly created page object on success.
Otherwise, it returns Nil and the error handler is called.
#HPDF_INVALID_DOCUMENT - An invalid document handle was set.
#HPDF_FAILED_TO_ALLOC_MEM - Memory allocation failed.
#HPDF_INVALID_PAGE - An invalid page handle was set.