The final patterns of things I design will be drawn up on the computer. However when figuring out a design I like to doodle on graph paper. I like GRID 8 x 8 where there are 8 grids per inch.
I don't like to buy it. For the price of a 50 sheet pad I can buy a ream (500 sheet) of computer paper. So I print my own.
Just open the PDF and print it. The grid is in blue. If you print in color it will not be overbearing to your doodling. If print in black and white it comes out less intense than if the grid were black.
If you have drawing software you can make you own graph paper and customize it for your specific needs. (Different grid sizes, different grid sizes in each dimension, Make some lines bolder, etc)