How about changing the content of the 'browse' button?

You can change this by going in to properties and editing the Button Text property.

First click on the gear icon of the File Upload tool, click on Show Properties. Look for the Proerty Button Text (first one on top). Type in your desired label.

This is my example form:

http://form.jotformpro.com/form/40955307195964?

Do let us know if you need further assistance, thank you.