If you would like to have a pattern piece that stays true to size longer and can be used over and over try printing it out on interfacing. I used Craft Fuse which is what I had around to try. It is heavy but not too heavy. It has a fuseable on one side and I printed the pattern on the side that is plain. I have tried a lighter interfacing for other projects but it should not be too thin or it will jam in the printer and will not hold up as well for multiple pinnings. Make sure your printer does not use heat to print or the glue will melt and ruin your printer. You could look for a craft interfacing with out fusable.
If your printer will not print on interfacing you could lay you interfacing over your pattern and trace. Use a permant marker and a ruler for straight lines to be more exact.