Milk supply is based on demand and supplementing with formula, pumping or using a pacifier may negatively affect your milk supply. (myorganicformula.com)
The use of a pacifier could also affect your milk supply if your baby isn't breastfeeding as much as he normally would because he is using the pacifier instead. (verywellfamily.com)
Both of these can adversely affect milk supply since the milk will not be removed from the breast well. (motherandchildhealth.com)