I added the wrong shipping on an item. I already sent the invoice. How do I void that invoice and send another?

what do you mean you added the wrong shipping?  Did you put the shipping that was in the listing?  You can't charge the buyer more for shipping then the listing stated - that is against policy.  Unless it is an international shipment and you didn't have the amount on the listing.   You can lower the shipping amount but not raise it. 

You don't have to void the invoice.  Just go to your sold page, find the item and on the right under more actions should be the link to send invoice - and you'll just send them a new one.  Otherwise you can go tht the order details page and use the drop down box. 

bidded - (v. nonstandard) Simple past tense and past participle of bid - (Wiktionary)

You can charge the buyer the same shipping as shown in the listing or less. You cannot charge more than was in the item listing. That a policy violation and a good way to be reported to eBay and earn negative feedback and low DSRs.