How can I print this PDF and fill an A4 page? I have this PDF. It's a simple grid created in Pixelmator with lines every 500 pixels. I want to use it as a template for drawing over a Wacom tablet.

For some reason, no matter what I do, print preview won't display the full grid. I've tried changing scaling, etc to no avail.

The image is 2880 x 1800 (the resolution of my MacBook Pro Retina 15").

This seems like a really simple thing to do...
It is not really a glitch.

The accuracy of print preview depends on 2 factors.

One is the Printer it self. 

Try changing printer type or select high print resolution (1200 DPi or more).

The second factor is the application showing the print preview.

If you for example use the Adobe Reader it shows much better print preview then Preview.app it self.

Example: