It is customary for the family of the bride to shoulder the financial burden of paying for the wedding invitations. This, however, can change depending on the specifics of the situation as well as the preferences of the pair. It's possible that some couples will decide to split the expense of the invites with their families, while others will opt to pay for them all on their own.
In order to avoid any misconceptions or disagreements regarding who will be responsible for paying for the invitations and other costs associated with the wedding, it is essential to disclose this information to both your partner and their families. It is also a good idea to address your budget as well as any financial issues from the beginning of the process so that everyone is on the same page.