The problem with resizing usually comes with the stitch density as sarge1 mentioned. Most designs can accomodate 10-20% increase or descrease without problems. If you have software with your machine, there should be some info as to its capabilities and limitations.
Also most embroidery designers offer their work with this already taken into account and allow you to purchase for your specific size hoop or multiple sizes for a slightly higher cost. You can always ask them before you purchase.