Genetic counselors are trained to answer these sorts of questions, but here's my answer.

One possibility is that your partner's father and grandfather carry(ed) an inherited mutation that increased their risk of developing pancreatic cancer. There are still mutations like this that have not been characterized by scientists, and so are not reported by the current genetic tests. If this is the case, then there is a 50 percent chance that your partner also carries the mutation. So frequent screening is a good idea. It is also possible that the fact that the father and grandfather both had pancreatic cancer is a coincidence, in which case your partner would not have an increased risk.

My family has a similar problem with a different type of cancer (strong family history, but no known cancer-associated mutation in the one living affected individual-me). I wish I could identify the mutation so that my other relative could gauge their risk. I had my whole genome sequenced, but there's too much information to figure out what to do with it (and I'm a professional molecular biologist.)