Printing a scan in original size

Hello,
Hopefully someone can help me? I have an Imac version 10.6.7 with an Epson NX420 all in one printer that I also got from Apple.
My problem is I cant figure out for the life of me, how after I scan something I cant get it to print in it's original size. Everytime I hit print it starts to print larger than the original.
The instructions say to use Preview to scan, which I can do okay. But it gives you no choice in how to save it. In this case it saves it as a Jpeg file on my desktop.
Once it is there , I can find no adjustment in Preview to reduce or enlarge this.
All I want to do is get a one to one copy, but it would be nice to know how to reduce and enlarge too.
Any help would be appreciated.
Thanks,
Jim

Drag it into something like Text Edit/Pages/keynote etc etc and size it there.

That's one way. Another way is to adjust the print dialog box so that it prints at the size you want.