I would like to know which operations in PDF page rendering (for a common technical book) take the most time. Is it font rendering? Is it objects parsing? Is it graphics drawing? Or what else?
In my experience, parsing is a minor, minor cost. PDF parsing is I/O bound. In the original version of Acrobat JPEG decoding was one of the largest costs, if you had images that used DCT (since FPUs were not standard). Antialiased font rendering was expensive at small point sizes, unless Greeking was turned on. For every high cost item in PDF rendering, there was usually a mechanism to mitigate it (font caching, Greeking, path caching, idle time page rendering, etc).