I'm using Processing 1.5.1
The operating system is XP SP3
The hardware is a Sony Vaio VGN-FE21B


I tried this code, found at: http://processing.org/reference/libraries/pdf/index.html

Multiple Pages (No Screen Display)

It's possible to write every frame as a new page in the PDF document. This example creates a 100 page document:

1. import processing.pdf.*;
2. void setup() {
3.   size(400, 400, PDF, "filename.pdf");
4. }
5. void draw() { // Draw something good here
6.   line(0, 0, frameCount * 4, height);
7.   PGraphicsPDF pdf = (PGraphicsPDF) g; // Get the renderer
8.   pdf.nextPage(); // Tell it to go to the next page
9.   // When finished drawing, quit and save the file
10.   if (frameCount == 100) {
11.     exit();
12.   }
13. }

and what I got has been a 101 (?) pages PDF (the last one blank).