In the birth record of daughter Elsa the wife of tailor Pehr Brandell is Catrina Olsdotter (abbreviated as Olsdr) Piteå landsförsamlings kyrkoarkiv, Födelse- och dopböcker, SE/HLA/1010154/C I/4 (1764-1782), bildid: C0035051_00241.
Their marriage should be in the same book if you browse back in time. The book seems to have births on the lefthand side, marriages in the narrow column on the righthand side and deaths in the broader column on the righthand side, keeping all events in parallell.
Olofsdotter and Olsdotter is the same thing. Karin and Katarina is the same name, may be spelled with a C or a K and with or without an 'h' in various places. Spellings weren't standardized, and the people themselves had no preferred spellings, they usually could read the bible but they couldn't write.