I am sorry if this got to be a little long-winded, guess that is the former teacher in me coming out. Enlarging a pattern with your home printer is actually pretty easy once you figure out the basics, but first I must ask you two questions:
1) Does your printer have a "copy" function? Almost all of them do nowadays. If not you'll have to get outside help. If it does, continue with question 2.
2 What is the size of the pattern that you are trying to copy? If you have a standard printer and the original pattern piece is 4x5" or smaller, you should be able to enlarge it in one step.
--First of all, mark a line exactly 1" long on the front of the pattern piece. Trim most of the surrounding paper from the pattern, leaving only the pattern and a seam allowance if it isn't already included.
--Place the piece you want to copy face down in the corner of the glass bed with the highlighted or colored edge. If the pattern piece is not square, put the longest side of the pattern parallel to the longest side of the glass. If it is not placed in the correct corner, it will not copy the entire document!
--Press the copy function button. It will probably ask what you want to copy, Select "document".
-- Although every brand of printer is a little different, the basic process from here on should be pretty much the same, but the terminology or function symbols might be different than my HP. There should be a "button" on the screen that opens up the settings, options or properties of the copier. Mine looks like a little sun with a grey dot in the center. Press that button. A new screen should appear.
--This section will allow you to choose the paper size, if you want to print on both sides of the paper, or if you want to resize the original. If that is what you see, Bingo!! You're on the right screen. Press "resize" .
--Next it will ask if you want "custom" or "fit to page". Select "custom".
--A box should come up that will let you set the percentage that you want to enlarge to. Set it at 200%.
--Hit "done". You might have to go backwards to the page that you found the settings button and select the number of pages that you want to print. Press " print". Your copy should come out to be 200% of the original. If it is off one way or another, redo the sizing either up or down a little to get to the correct size, and reprint.
If your pattern is larger than 4x5":
--You will have to enlarge the pattern in sections and tape them together to get the correct size. That also, isn't hard once you've done it. You just have to prepare the original piece for enlarging. Determine how large your pattern will be after it is enlarged to 200%.
--Cut your original pattern piece into 1/2, 1/4s, 1/3s or even 1/8s so that when you make them twice as large, they will fit on to an 8.5x11" page, remembering that they will not copy all the way to the very edge.
--Mark on both sides of the cutting lines with hash marks, xs, or symbols so that you can easily match up the original cut line and/or the shape as you reassemble the pieces.
--Enlarge each piece just as you would for a smaller item. Tape the sections together matching your markings, removing some of the excess paper if necessary. You're done.