That depends on what it is, I'd say.
It could be just a piece of text in a barcode font. Then you can't change it, like you can't make a text in Arial higher while keeping the same width.
And it could be a figure. Then try right click on it, and see what you can do in it's properties.
Difficult to tell without having the document at hand.
Here is my problem with Microsoft Office Word 2003. I have pasted a bar code from another site. I want to make the height of the bar code lines longer. I know that if you simply make your own line with the drawing objects and double click on the line you can change the length and such.
But having pasted this set of lines (Barcode) it won't allow me to click on the lines and make them longer. Is there a way to make an object longer (going vertical not horizontal)?