Hello,
HikaMarket do not override the HikaShop invoice design but it can override the "store address" that you see in the invoice.
That override is only made for the front-end customer invoice and only if you have the vendor limitation in the cart and only one sub sale.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.