n_pages
Description:
The number of pages in the document.
This must be set to a positive number before the rendering starts. It may be set in a begin_print signal hander.
Note that the page numbers passed to the request_page_setup
and draw_page signals are 0-based, i.e. if the user chooses to print
all pages, the last draw_page signal will be for page n_pages
- 1.