Remove +- signs from quantity

It's not there. In the config, under the display tab, you have the option "Display the quantity field on the product page" for that :
www.hikashop.com/support/documentation/54.html#display

If you just want to remove the + and - without removing the input box, then you can add the CSS code below to the HikaShop front end CSS that you can edit in the configuraiton under the tab display:

a.hikashop_product_quantity_field_change{
	display: none;
}