How to size up a pattern using photoshop

Because I had a lot of trouble figuring out how to do this.  And drawing it out by hand can be a drag with all of those squares and boxes and arbitrary lines, especially if one pattern piece is smaller and very complicated as to curves and darts.  So without further ado, here's a poorly explained tutorial about sizing up little patterns to scale!

I'm going to start out using this pattern I scanned from Moden: 1840-1890.  Unfortunately, it's in Danish.  Fortunately, that isn't really important.

 It's a bit poor quality, but most patterns are if you scale them up 2000x their normal size.  You're probably going to have to clean this up once it's printed out...

Take a screenshot and open it in photoshop!

You're going to want to make your canvas really large in order to give you lots of room in case the finished product is bigger than you expect.  I don't expect the bertha's going to be anything over 50" x 50", so that's what I set it as.

Select the part of the pattern you're working with and select it with the square marquee tool.  Go to Edit>Free Transform.  This is only if you don't know the exact scale, i.e. 1/8 of the original scale.  If you do know the exact amount you need to scale it up by, skip ahead.

Here's the funky and arbitrary part.

This is all I have in terms of scale: 1 box = 5 cm., which is about 1.96".

Meh, close enough.

So now that I'm in Free Transform I can grab my picture and make it smaller or larger.  I use the ruler tools on the side as a guide - I know one box is a bit less than two inches so I try to make it as close to that as possible.

Once I'm satisfied with resizing the width, I look at the top of the screen and notice what the magnification for the width is.  I then type that into the box with the height magnification, as well.  The picture should now be at the same scale as it was originally.  If you already know the magnification, just type it into those boxes once you're in free transform (as in, if the pattern was 1/8 scale, make the height and width 800.00%.)

Now that you have your resized pattern, it's time to split it up and print it out (unles you have a kinko's size printer at home, that is.)

 Select a piece of the pattern (I start with top right) and select a portion that's under 8.5 x 11.

Copy this and open a new file.  The new file should be the exact dimensions of the piece you just copied, so click Edit>paste and the portion should come up.

Wa-lah!  Now you just need to do that for the rest of the pattern, then print it out (don't worry if 'some clipping may occur,' it just means you get to do some fancy guesswork as to where things go) and tape it together like one big jigsaw puzzle.  You can go ove the blurry lines with marker if you want.  The trick is not to do anything too big, but it goes quickly once you've got the hang of it.
Feel free to ask questions!  I'm happy to procrastinate about not wanting to sew my stays.  After 100 something boning channels I'm less than enthused.