Ok so now that you've tried the first way to grade a pattern I'm going to show you an even easier way. This way isn't always appropriate. For instance I find it's better for grading up than it is for grading down... It's much better for larger pattern pieces than it is for smaller ones
I managed to do all this AND blog about it during the girl's nap-time!
First you'll need to collect your supplies: Paper, pencil and your pattern. (Good light helps a ton too)
Lay the paper on top of your pattern and trace the largest size. I also like to trace the next size down so I know how much to adjust between sizes. This is going to be a template for you to use in the next step.
Once you're done tracing, lay the pattern on top of the template. Line up the largest size on the pattern with the second largest size on the template so that you can see where the next size up belongs. Trace the template onto the pattern. You'll need to extend it in the same areas where the size goes up between other sizes - this means you have to do this in sections.
Use this template to extend all the edges that need to be extending (again any edges on the fold doesn't need to be extended)