As others have pointed out, Catholic teaching requires a married couple to at least be open to the procreation of children in their marriage.
However, I don’t think we have to interpret that to mean that a couple who are capable of having children naturally should always foreclose the possibility of adopting children. Especially if the couple feels a strong calling to adopt a child who might otherwise be hard to place for adoption (an older child, as the OP specified, or a child with developmental disabilities) that can be a selfless and loving expression of their love as a family. I have also know people who were adopted as children who as adults feel a strong call to adopt, to open their home to a child in the way their parents opened their home to them.
Essentially, if the OP is married or contemplating marriage, this is something she would have to work out with her husband in the context of their marriage vows, which require them to at least be open to the possibility of having children naturally. If she is single, I know of no church teaching that would prohibit a single person from adopting a child, if that is something she feels called to do.